I have met some amazing people through CF, and I would certainly class a good handful of them as actual, proper friends.
Having theme parks in common is a great ice breaker. Even if I don't share the same outlook on life and values as somebody else, there's always coasters to fall back on. By seeing somebody talk passionately about a particular ride or park, it's usually a good way of learning a bit more about their personality, likes and dislikes. Over time, such conversations do tend branch away from theme parks and the person reveals themselves and friendship can blossom.
Thankfully I've met some similarly minded people through CF, and others who I can learn from and (hopefully) they can learn from me. I think that's where friendships really develop - what you can offer and take from each person.
People always fascinate me and CF has a nice mixture of people that I certainly would not encounter in my everyday life. I think that has certainly improved my life.
How has it affected my social life?
For starters, it's widened it. I have a solid core of local (non-CF) mates and as much as I enjoy their company, what we do together can be limited, although it's always fun.
Without getting to properly know certain people from this site, I wouldn't have had many wonderful, eye opening and off-the-wall experiences.
I don't like to socialise on the internet, which is why I'm rarely on MSN, not publicly on Facebook and don't bother with Skype or other crap like that. I'd much rather see somebody in person, watch their facial expressions and gestures as they talk, actually physically experience their personality.
There have been times in the past when I've been low and considered jacking in CF but keeping in contact with the good mates I have made through it.
But no, if I jacked in CF, then I'm less likely to meet another Martyn, Karen, big john, Tanya, Mark & Marc, Vadge, Sam, Pierre, Rob, Kir, Slayed, Leighton, themeparkphreak, Snoo, Rach, furie, Joey, Jerry, Mandeerrrr, Ben, Jake, Collette, Gay-but-not, Stone Cold and so on......
(Btw, that's not a definitive list, just several examples.)