I homeschool an only who is also an extreme extrovert! Socialization is not a problem, though it does require time and gas money. We have weekly park days with our homeschooling charter, classes on site, private classes like Lego Robotics and homeschool PE, plus he is a competitive fencer and spends at least 4 (usually 6) hours a week at the fencing academy. He plays minecraft online with friends, skypes with other friends, works on cooperative stories in google docs with yet other friends. We go to the library, do tons of field trips and he spends hours a week just talking to random people!
I'd say that he gets FAR more time socializing with a much wider variety of people than he did sitting in a classroom (for K-3) with his age mates and *shhhhh* quiet, we're teaching! His school had 15 min of recess in the morning, plus a whisper lunch, so it wasn't exactly the hotbed of friendship development anyway!
