I know that this question tends to come up every now and then, but I've never really managed to pin down and answer. On the one hand some people see fairly relaxed about getting there steel frames pretty wet (when I mentioned on here that I was using FrameSaver on a steel frame I was told it was a waste of time) but on the other you do hear of frighteningly thin tube walls, folks that find a pint of muddy water sloping about inside their frames and chainstays etc. rusting through.
So what's the general view on steel frame care? Clearly if you've been out in a torential storm removing the seatpost and leaving the frame upsidedown to drain is a good idea, but what about general rain and drizzle, I think that I might be being a little over-cautious. Presumably a small amount of water that finds its way into a frame will evapourate out once the bikes in the warm and dry (I was told never to seal over the breathe holes in a steel frame for this reason, by a bike shop owner).
And no, I don't fancy drilling a hole in my bottom bracket shell (although I can see the sense).