Well, I wasn't particularly suggesting that.
Wiki does nofollow all outgoing links, and apparently it doesn't HURT their rankings.
But I would use a link as an editorial vote - which is what google WISHES we would all do. If you like / love a site, give them a vote with a do follow link.
Don't give them a link JUST to return a favor, or manipulate page rank, etc.
netmeg posted in another thread that she gives out dofollow links to sites that she thinks would be useful to the visitors to HER page. That's probably what google wishes all web owners would do.
I've been around long enough to remember when people had small personal sites on geocities and tripod and whatnot that looked like carp, with blinking graphics and scrolling text and an obvious dearth of optimization.
Those sites would often have a page like: "Other sites I love" and would link out to, um, other sites that they loved.
I think that is what google wishes web site owners would do: link out to other sites that you love.