In my opinion a bounty is a great way to revive a question but I'm just wondering whether displaying the reward value may sometimes cause any disservice to the question itself.
I've seen some high-value bounties attracting a fair share of "junk" answers for the sole purpose of collecting rep points. For non-bountied questions, down-voting is somewhat an effective deterrent, however depending on how much is at stake, taking a few hits may be well worth for some.
We need to educate these users of course, but do you not think that knowing that there's an extra prize to win is enough? It also adds an element of surprise which could be nice.
I appreciate that this would definitely encourage some people to provide the bare minimum value as a reward. Perhaps the reward value could be displayed to "established" users only? (e.g. above 3K rep points)