The US Government cares, particularly those involved with the United States Code. I highly recommend you read Title 18, Sections 2256 and 2257. The law explicitly states that it is illegal to depict minors involved in sexual acts.
Section 2256:
http://www.law.cornell.edu/uscode/ht...6----000-.html
Section 2257:
http://www.law.cornell.edu/uscode/ht...7----000-.html
The grey area, of course, is what defines a sexual act. For a number of us here, the mere showing off of a male foot causes a sexual reaction. If a sixteen-year-old is pictured showing his feet, that could possibly be construed as engaging in a sexual act, regardless of the photo subject's intent.
The management of FootBuddies would prefer to err conservatively. The cost of legal battles is astounding; and the price for losing is a mandatory five-year prison term for a first offense. I think I speak for the entire management of FootBuddies when I say we'd rather not chance that.