Originally Posted by
Continuity
I read about how someone got an old frame where someone had placed a wadded-up rag down the seat tube, presumably to stop water/gunk from getting down to the BB, but the rag had the unfortunate effect of holding moisture at the point where it was wedged in the tube, and led to it rusting out in that area, from the inside.

That might have been me, I had a beater bike that died that way. A quite surprising experience.