If on a site you enforce that each user is only allowed one bitcoin address that isn't publicly visible, could there be any unforeseen issues? AFAIK it should be OK- if someone discovers their bitcoin address then they just make a new one and get a new username. And if someone DID get their bitcoin address, all they could do is view their transactions using that address.
Am I correct?
Why limit it. There are plenty for everyone. Its not like you'll run out.
Ya the main effect is they lose what privacy they could have with multiple addresses. It's not a matter of someone accidently discovering the address. It's that anyone they want payment from will need to have it and thus will have access to the full list of transactions on that address.