I been homeschooled all my life, and I feel that it's actually made me MORE social. I was in charter/homeschool K-8 and then full on homeschooled through high school. I've made plenty of friends through the charter school, and also through local music festivals, fairs, etc. I have plenty of friends that I hang out with regularly, just like any other kid. Idk about full on homeschooling for K-8 though. I think the charter school really helped in the long run.
It really comes down to how well the parent does, and the child's attitude towards it. I've met some pretty antisocial kids, but the majority of homeschoolers that I meet are fun-loving and rather adventurous, especially since your schedule is a lot more open for trips and field trips, and other such activities. As long as you can nail down at least a few solid friends, it's a really great way to go....