I agree with Rystil. I'm strongly opposed to Judges receiving anything like DM credits or Judge credits for doing their judgly duties. I'd feel like a congressman voting to increase my own pay. I judge because I love D&D and LEW, not because I want anything back. And I especially don't want the non-judges to feel underprivileged or whatever.
That being said, I think that offering a small incentive to all people equally, judges and non-judges alike, for helping with a massive task (such as summarizing adventures!), is a good way to get some administrative duties done without adding more people to the judges team and/or overburdening the judges.
The operative word being "small". I think that A) people are doing it already anyway, for free, and B) the primary means of improving your character (as Manz said) should be through adventuring.
To give an extreme case, let's look at ATfL on Rystil's misconceived 'Nock-scale. For giving up a Saturday afternoon, I get 60 DM credits. (For perspective, that's equivalent to 5 years of DMing an adventure.) So now I apply that to Razh, my L5 dwarf. 10 DM credits gives him 2500 XP ( [5*50]*10 = 2500 ), bringing him up to L6. Then I spend 17 more to get him 5100 XP ( [6*50]*17 = 5100 ), bringing him up to L7. Then I spend 20 more to get him 7000 XP, which jacks him up to L8. Then I spend my remaining 13 to give him 5200 more XP.
So suddenly, in one day, my L5 dwarf is now L8, and half way to L9.
What?! 
I don't care how good my summary is, it took me 3 years to get him to L5, it should not take me one afternoon to get him to L8 and a half.
So I'm pretty strongly opposed to anything more than a few DM credits.
B4cchus raises an interesting suggestion, about rewarding based on summary length. I have three problems with this, though. A) Quantity does not equal quality. (But a judge will look at it, you say. See B.) B) A judge will have to look at it.

I'd rather not have a judge position be "reviewer of summaries". And C) Even if a judge looks at it, this is still volunteer work, and it's very hard (and usually rude) to tell a volunteer, "Uh, thanks, but no thanks."
Hmm... So I guess, in summary, I prefer a small, simply determined amount of DM credits, based on either real-time duration or number of posts.
If everybody really likes 'Nock's table of values (which is very fair, I think, but a little complicated for my tastes) you can outvote me. Or persuade me and tell me that I'm being dumb. Either way. =D