I don't play Facebook games and zynga games especially because I don't like that every time you login it asks you to send spam messages to everyone on your friends list.
^^^^ This.
Micro-transactions and DLC are sorta irritating, but I think they're a legitimate business model in the right context. (For instance, Rock Band's use of DLC makes perfect sense--rather than pay for a bunch of songs you don't want, you buy the ones you do want and slowly build your custom tracklist. Better than having to slap down $20 several times for "expansion packs" full of crap to get a handful of musical gems)
I've played a number of Chinese-based browser strategy games that use micro-transactions as well, and they're balanced enough that you can still have a decent game without buying extra crap. Yes, you won't be in the top tier, but if you're in a solid clan it's not that much of a problem.
My main problem with Zynga games (and most Facebook games, to be honest) is that they want you to leverage your base of friends by "adding" them into your game with a shitload of invites and then spamming their pages (and your own) with updates. Thankfully, they've made it easier to hide that shit, but for someone like me, having to spam my friends in order to advance in the game ("Invite 25 friends to unlock next level!") is a non-starter.
I think Playfish is an example of a decent Facebook game dev. While they do have some that use micro-transactions (or they have "premium" paid versions of their games), they're mostly solo games. And they tend to be a bit more brain-teaser and/or educational (brain teasers, geography quizzes, Scrabble-type games) rather than just "how much crap can you collect?" like Mafia Wars.