[glenbo]

I agree that meetups, open source and friends can help with mentorship, but being forced to solve problems in a group is a lot more effective than casual encounters and meetups.

That said, it probably depends on the type of person you are. If you're super outgoing and involved, freelancing full-time is probably similar to working at an agency in that regard, but if that's true it sort works against the point of your post.