When Stan was written, Eminem had only 1 album out. It's a brilliant song, of course, but was he famous on the level where someone would be obsessed with him?
I don't know how big and popular Eminem was with SSLP alone, but I always felt like he wasn't THAT famous that someone would stalk him and kill himself because of him. It would have made more sense if Stan was released after MMLP, when he was the biggest celebrity around.
Don't get me wrong, the song stands on it's own no matter what. It's just that it seems a bit premature at the time considering he only had one album out.
I may be underestimating how big he was when SSLP came out.