I've heard it said that this spell is almost in the campaign-breaker realm, as it can nearly replace a social oriented character if youre smart about using it. Namely make suggestions that are hard to provide evidence against and its almost a guranteed sell. as to erasing memories I'd have to say no, but convince someone that his memories have been tampered with by someone else sure. He wont forget what he remembers but he may not believe it to be the facts of the matter anymore either.