I imprinted my foals, and they were turned out with mom and the herd...BUT, I would still go out and mess with them every single day for short periods. I would fool with their feet, put a halter on them every day (I NEVER left it on them unattended)....just little things. By the time they were ready to bring in and wean, they already enjoyed being handled, and there were no surprises for them because they were already accustomed to everything a weanling is expected to do.
It doesn't matter how big your pasture is, as long as you have hands on them on a daily or every other day basis to keep them familiar with human contact. It's just as important for them to be out in the fresh air and sunshine so they can grow, stretch their legs, learn coordination, etc, so I definitely advocate the whole "growing up in the pasture" scenario...just not the growing up unhandled and wild.