I've done several trips on the bike and have had no issues with my cameras. To save space I usually skip the camera bag and just have the camera mixed in with clothes.
Bike riding is the main reason I bought a 4/3 camera. The image quality is almost as good as an SLR and far better than any P&S but it's much smaller than an SLR. If I didn't have teh 4/3 I'd do like LoneRider and get an EOS-M. It is perfect for this, IMO.
I also carry a small P&S on a lanyard and sometimes use it for pics while riding. The occasional, random, over-the-shoulder snap can be interesting.