Around half my friends in total and about 2/3 of the people I've gotten to know since coming to college are girls. The one relationship I've had evolved out of a friendship, and I've had feelings worth remarking on for 2 others at times during the last 3 years. So, I'd say that it is more than possible for opposite-sex friendships to exist. There is always the POSSIBILITY for one person to get ideas of more but it is by no means the expected outcome.