Assuming that continuing to earn votes after hitting the daily reputation cap is considered a "Good Thing" (i.e. a behavior that the site would like to promote), I think it would be nice to think of something useful that could be done with all this over-the-cap reputation.
One example could be offering badges for earning
N over-the-cap points for
K days (say, the usual 1-50-150).
N should be picked high enough as to avoid giving these badges automatically to everyone who hits the daily cap; I'm thinking "200 over" should be a reasonable pick, but perhaps it should be even higher than that.
Another example could be offering over-the-cap reputation to set bounties at some draconian exchange rate (say, 20 over-the-cap points for each bounty point you offer on someone else's question, or 40 over-the-cap points for each bounty point that you offer on your own question). So if you have 2000 over-the-cap point, you could offer a 100-point bounty on someone else's question, or a 50-point bounty on your own question.
What do you think?