I mean that use of them is about as solitary as games get, and the prevailing reason they're known as "social" is because of artificially engineered spam-your-friends-to-advance mechanics. I play a particular RPG on Facebook -- beating some monsters requires getting 100+ folks to click on a viral link for you. We've got our own little social norms and lingo for dealing with that: I click on your link and tell you "PRTF http://example.com/12345 -- for "please return the favor", because since I'm telling that to several dozen people I don't know and don't care about every day I'll be darned if I actually type it out.
None of my friends have ever come over in real life and told me "Patrick Patrick guess what guess what I got a new FarmVille cow." That would be really, truly social for me. (And I say this as somebody who regularly hears stories about WoW loot or D&D games from days gone by.)
To keep with the anecdotes - I have friends who when they meet up normally pull their laptops out for some farmville (and to plan how to get the next level/cow/whatever). It does happen.
But great observation on the iPhone games thing - one of the discussions at our extended family dinner every couple of weeks is the new iPhone/iTouch apps we have.. "Hey check this out" is really effective marketing (as of course it is in every industry)
None of my friends have ever come over in real life and told me "Patrick Patrick guess what guess what I got a new FarmVille cow." That would be really, truly social for me. (And I say this as somebody who regularly hears stories about WoW loot or D&D games from days gone by.)