Not terribly. The biggest danger of using a ribbon mic on a bass cab (or anything else, for that matter) is a large volume of air striking the ribbon directly and blowing it out. A player with a loud amp unplugging a bass can produce this pop, but tamer volume situations aren't too dangerous. If you check out Wes Dooley (AEA)'s site, he's got a tutorial on close mic'ing a kick drum with a ribbon mic (I've done this once, and it sounds freakin' amazing). One of the best mic'd bass tones I've recorded was a jazz-bass special into a fender champ mic'd with a Reslo ribbon (mid '60s, entry/mid-level mic). Sounded larger than life, but in the room wasn't much louder than a speaking voice.
That said, I've had good results with the apex 460 tube mic (cheapie) on an ampeg sb12, and with audix scx-1s, but my all time fave is a decent DI into a decent pre. Better is, well, better, but decent is usually excellent.
The exception being if a player uses a lot of effects, especially overdrive effects, an amp takes the edge off better than I can do with EQ later.
