Riding on a failing bottom bracket - what could possibly go wrong? My BB is showing the first signs of being on the way out (a click when I drive either foot down hard; if I remove the chain there's a barely perceptible clicky feeling at the same crank position as the click).  It's not convenient to get it fixed in the near future.  The last time I wore one out, the ride was horribly notchy by the time I got it done, but I blamed the cassette/chain.

What's likely to happen if I keep riding on it?  I can tolerate a rough ride on this bike (I'm not doing much distance on it at the moment). But I don't want to damage anything else (this seems unlikely to me).  I also don't want a sudden failure, especially one that causes things to seize up.
Eventually your bearings will disintegrate and your BB will lose its ability to hold the spindle centred withing the BB shell, that will result in the crankset becoming wobbly, your chain will come off, your chainring might even go hit your chainstay and if you're lucky it will happen at low speed.

Here's a BB I personally exploded on my fixed gear commuter



Everything I described above happened and I would not recommend running a clearly faulty BB for too long.

I believe a BB using bearing cartridges might not fail as catastrophically as one with simple cages like the one pictured but I doubt it would end well in the long term.