1) For selfish UCC, take note of
Delicious' example and try to drive general relevance without
interrupting the selfishness of your users. Delicious
prompts me with terms others have used, making my selfish life
easier while making relevance of my actions more general.
2) For social UCC, create
programmatic mechanisms (like polls or votes or star ratings) that
allow people to quantify their point of view on some abstract
scale. This will benefit the user (by allowing them to say
simply, "I am *very* Republican," for instance) and benefit
everyone else -- who can then say, "He's *very* Republican, and I
can easily assess where he's coming from."
3) For Selfless UCC, use human
editors to manage quality, and try as much as possible to create
"superuser" editors to do this for you. The cost-benefit
ratio is outstanding, so get over the stone-ageness of it and go
make money.