If the NCAA is going to enforce this rule, it is going to have to figure out if a particular username is really a fan of that institution or not.
What I'm saying is that opposing schools' fans could POSE as Husker fans and make all kinds of inappropriate contact (in the name of Husker Nation). Similarly, Husker Nation (if we weren't such nice, upstanding citizens), could create Twitter accounts like Whisky4EVAH and inappropriately contact Wisconsin recruits pretending to harass them to attend Wisconsin, in the hopes of getting Wisconsin in some sort of hot water.
Do you really think the NCAA wants to police/investigate this stuff? The schools, on the other hand, have to go through the motions of trying to get their fans to comply with an unenforceable rule, because NOT trying would make them more likely to be wrist-slapped, or worse.
In short, we now return you to your regularly scheduled life, already in progress.