A friend of mine made a deposit in a sperm donor bank prior to getting a vasectomy. Two years later, he met a woman, who he dated for a few weeks before breaking it off.
9 months later, he was presented with child support demands from the state. She had stalked him, determined he had made a deposit in the sperm bank, then specifically chosen his profile to get pregnant.
He is now liable for child support, whether he likes it or not, for the rest of his life (California, in case its of importance). They didn't have sex - she stalked him, got artificially inseminated, and then went to the state to extract money from him. He now has a kid he never wanted, and is resigned to being a father to the child, even though he never planned it and it was forced upon him by a criminal stalker.
This highlights just how dangerous it is for men to use these services. Clearly, more regulation and oversight is required - especially if sperm banks are making their own decisions about how their resources are applied.