My own "feeling" is actually the opposite is true. My 6 home schooled friends are far and away the most socially adept people I know. Super friendly and able to talk to anyone. The 5 home schooled kids I know are similar. If they were at high school you'd expect them to be among the most popular people as they are so friendly and outgoing.
Here's another anecdote of you care to listen
http://www.thisamericanlife.org/radio-archives/episode/177/a...
Here's reference to one study that claims home schooled kids are indistinguishable from public schooled kids
http://www.pbs.org/parents/education/homeschooling/socializa...