So many great tipps, but I couldn't find one answer: How do you guys handle rain?

I don't mean riding in the rain, I mean the effect of rain on your bike. It always bothers me keeping my bicycle out in the rain, for fear of lube washing off and rust. But is it worth the hassle (and weight, about 750g), to pitch a rain cover every night?

How do you do it, do you keep your bicycle dry whenever possible, or should a bike handle a bit of water?