It's a humor meter for me. Make me laugh (easier said than done) and you'll get one. An example, my latest one was given for a person who replied to a post that said "It's not illegal, just frowned upon" with "Like masturbating on an airplane?" Movie quotes get me every time!
Or if somebody provides a thorough post that expresses my ideas identically, I'll kudo instead of just repeating what they say.
Kudos are like trophies. They don't mean anything, they're just a little something extra.
EDIT: Huh. 65 kudos received, 30 given.
I would tend to disagree with this. Trophies you earn for yourself. Earning the respect of your peers is how you get Kudos.
There's certainly nothing wrong with earning your fellow gamer's respect because it not only means you contributed, but that contribution was important to someone else in some way or another.
Now when it comes to being proud, i can see where trophies and Kudos would be alike.