About all the "bandwagon fans" that have joined Red Sox Nation, I think some of you are a little off-base. Granted, I haven't read the entire thread.
I think it started with the new ownership, and new image of the team. Players like Johnny Damon and Kevin Millar came to Boston, and attracted a large female population (see: pink hats). People jumped on the "Idiot" image. Claims that people only became Sox fans when they started winning are not entirely true, as most of this stuff started happening in '03, before the Sox were even in the playoffs. They played .500 ball over the course of a few months and were far from guaranteed a playoff spot. NESN and the new owners really promoted the team though, and yes, making the playoffs and going to Game 7 in the ALCS helped solidify the new fan base, but it wasn't the only reason for their popularity.