Weartesting is definitely among the NCAA's no-nos. You can do it as long as you don't deal directly with the company, however (i.e. your coach works as a liaison for the program).
Most wear test programs will send you anything that matches the profile they're trying to examine. It can be very arbitrary (you could be a perfect candidate but be in the wrong part of the country or whatever). Also, these companies have HUGE testing databases to pull from so sometimes they'll send stuff to people and sometimes not. They will utilize testers that provide useful feedback more often, though, so be as constructive as possible.
"This shoe sucks" will NOT get you another test very quickly. Neither will, "Shoe was great." Details get you more tests, good or bad.