So it seems that Stack Overflow's reputation feature is used not only to distinguish members who have put more time into the site than others, but also as a spam deterrent.

Seeing as the privileges of a person with low reputation are extremely limited, and the privileges of an individual with a lot of reputation is vast, I was wondering how resilient this mechanism is to spammers.

Although there is a lot of frustration coming from new users, this mechanism seems to deter spam by preventing new users from posting links and editing posts without peer review. So that begs the question: How much spam does this feature prevent? I know this figure would be hard to estimate but I'm curious.

Furthermore, have there ever been instances on SO when people would pay individuals to farm reputation, that was later used for spam posts?

Edit: I forgot to mention that I'd like to forego the discussion of CAPTCHAs and just talk about the reputation system and it's effect on unwanted posts

So it seems that Stack Overflow's reputation feature is used not only to distinguish members who have put more time into the site than others, but also as a spam deterrent.

Seeing as the privileges of a person with low reputation are extremely limited, and the privileges of an individual with a lot of reputation is vast, I was wondering how resilient this mechanism is to spammers.

Although there is a lot of frustration coming from new users, this mechanism seems to deter spam by preventing new users from posting links and editing posts without peer review. So that begs the question: How much spam does this feature prevent? I know this figure would be hard to estimate but I'm curious.

Furthermore, have there ever been instances on SO when people would pay individuals to farm reputation, that was later used for spam posts?

Edit: I forgot to mention that I'd like to forego the discussion of CAPTCHAs and just talk about the reputation system and its effect on unwanted posts