Sure, when that bearing seizes the pulley stops spinning, and your belt snaps. When your belt snaps you get stranded. I just faced this problem myself, and there are people out there that sell rebuilt pumps. I bought mine for $195 from a place in CA that sells them on ebay, but there are others. A new one costs $1,000! Alternatively, you can get a shorter serpantine belt and bypass the pump altogether. I would have done this, but smog checks are pretty strict where I live, so I decided to get a replacement. Oh, and its an easy DIY job.

GregS
'84 300D, 183k
'90 300CE, 173k