That is exactly what happened to myspace. They kept adding features that pissed people off and trashed up the site.
Facebook came along as a clean and fresh blank slate where things were simple and you werent blasted with stupid music and glittery profiles every time you clicked on a friends page.
Google+ has a problem of just not being “cool” enough to use since none of your friends really use it. That’s the biggest hurdle and problem.
Granted if google+ figured out a way to get a lot of hot/young chicks on there the male population would clearly follow and bring popularity to the site.