[asdff]

Most people who I've seen winter biking are riding some beater $100 used mountain bike into the ground during winter over a nice bike. Remove the derailleur, and there are still a lot of components all over the bike that will get fouled up with corrosion, dirt, oily sludgy snow, etc, so its better to ride something disposable during that season.

[Valgrim]

I agree. My personal experience is that the chain and derailleur are by far the most fragile parts of the system (disk brakes are probably quite fragile too, but regular caliper/cantilever/v-brakes are not much affected by corrosion.) but on cheap bikes, chains are easy to replace and derailleurs have a lot of tolerance. So just cleaning them regularly and oiling them is generally good enough.

Some specialized winter bikes use a belt instead of a chain, but I find those too expensive, hard to service and maintain.