I highly doubt any employer would find the old stuff, but PI harvesting faggots might try to link a person's real identity to their online persona. I trolled a site so hard that several members said they were going to "dox" me and link my real identity with stupid shit I had said on their forum. I wouldn't want that shit linked to who I am. Not that many people are motivated to do something like that, but if it were to occur it'd be pretty awful. I've posted guides on anal sex, racism, stuff about bestiality and other topics I'd prefer not to have linked to my real name.