Since reputation is relatively 'cheap' to gain, it can be awarded to others 'for free', and can only seldom be lowered, does this mean overall reputation scores will get higher and higher and, effectively, become meaningless?
Even in this limited beta there are uses with over 3000 reputation earned in just over a month. I don't begrudge them,they earned that rep, but it seems if you can earn an average of 100 a day then it would seem in a years time you would have 30,000 rep.
So I think you are probably right, that it could become really high for active users. But the real question is if this is a bad thing. If a user really wants to make that kind of commitment to answering questions, then their reputation will reflect that. There are still a lot of users who do not have vary many reputation at all, so that means it does take an effort to get reputation.
So my answer is NO, it will not become meaningless, but it will be hard for late joiners to catch up with active users.
The point of Stack Overflow isn't to gain reputation.
Ultimately, this site is meant to be a wiki. Reputation's primary purpose is to serve as heuristics used to determine a form of worthiness or trust before allowing you editing capabilities.
That said, it doesn't mean there will not be idiots that eventually have as much power as everyone else, but hopefully there will be enough good people around to police the idiots.
EDIT: It's sad that people feel they should be rewarded for helping others - 7 years ago, I received a lot of help in Usenet newsgroups and tried to return the favor when I could, but did it purely because it was nice to give and receive help. Now people want some arbitrary number next to their name to be larger than someone else's? Help me live.
The point of Stack Overflow isn't to gain reputation.
Then I don't think you understand the rules of the game properly.
The site rewards high reputations, so it's absurd to suggest that the point is not to gain reputation. If that were not the point then there would not be any reward for high reputation.
I think that reputation (and voting for that matter) should decay over time, so that newer people have a chance to catch up. If someone stops using the site for a while, they should (slowly) loose rep points (I'd suggest exponential decay), because it is likely that etiquette will evolve, and they won't be used to the new style.
If there is an old discussion that has become stale, and the answer that has lots of votes is no longer true or relevant, a new vote should be worth more than the old votes.
It's sad that people feel they should be rewarded for helping others
I think you greatly misunderstand.
I contribute on plenty of forums that don't have stupid reward schemes. I don't need a reward at all. But if the extrinsic motivation is there it WILL destroy intrinsic motivation.
Good god, Joel himself wrote about this stuff. If you "pay" people to give answers, they will start giving answers only because they are paid.
Kill the reward scheme. Get rid of reputation. Get rid of badges. Get rid of user privileges based on points. Remove the extrinsic motivation.
I think it will become a problem, or at least, it will become less meaningfull over time for the reasons already talked about (it's linear, people who start early win, late comers lose)
It's almost like you need two displays for rep, the rep we have now (which you keep on adding too) and some kind of rep 'velocity' which basically shows how active you are in the community. This velocity would be the rep everyone sees beside your name, and could for example be the last 90 days of rep.
This both allows users to constantly gain rep and also remove the everest that presents to any new user who wishes to have a compeditive amount of rep.
Following on from some previous answers, I like the idea of some kind of 'rolling' reputation along the lines of the ranking system in tennis (and possibly other sports) - players' rankings are determined based on their performance over a rolling 12 month period. At each tournament they have to at least match their achievement the previous year or they lose points. If a player's level drops over time, so does their ranking.
Applying a similar approach to reputation, where rep drops over time if people's input decreases, means that latecomers will have a chance of catching up, and it will also differentiate between those who are active on a daily basis, and those who were active once but don't get too involved any more.
It will also get around another problem I envisage - it seems to me that at the moment as the site is so new, there's loads of questions being asked that haven't been asked before. Over time, as the database of questions build up, there will be fewer unique questions - people will either find their answers already here, or will have their questions closed as duplicates quite quickly. This will decrease the opportunities for earning reputation and give highly knowledgable latecomers no chance to compete with early arrivers, many of whom may be less knowledgable but will appear of greater repute. With a rolling system, the reduced opportunities to earn rep will affect everybody equally.
Finally, perhaps to avoid putting any noses out of joint, there could be one score for total rep ever earned, and another score for rolling reputation.
Yes, there is no natural cap or limit that we've been told, and it's linear progression.
But it's very simple to understand, which I think is key. They could implement a log conversion, or simply cap it at 10k or some arbitrary number, but that only makes more special cases.
Since there's a limited number of votes, everyone is policing everything, and there are limits to how many questions you can post (ie, once every two minutes or similar) then the damage a high point hacked account can inflict will be little and can be handled by the community.
Now, if someone hacks the top 50 accounts, they could probably ruin the front page for a day or so until Jeff shuts them out...
But I don't think it's a problem. The DOW just keeps going up, right? Why not stackoverflow reputation?
Besides, if you cap it (aside from eliminating e-size measurements) you also reduce some people's desire to answer questions. There are questions I answer only because I haven't hit my daily cap, where I wouldn't have because it takes some work and time to do right.
There has to be some payment for good work...
Should repuation points expire? Or perhaps only points earned in the last year count.
Otherwise when this site has been up for 10 years just about all the original members will have reached super-overlord level. This might discourage new members or lead to old-timer clique where only (then) ancient c# questions get voted up.