This is one reason why pro level cameras cost so much...because they are built to be able to handle a pretty good rainfall and keep working.
If you don't have a pro body, some care should be taken but life is too short to hide everytime it rains a little.
Example one: I was in Costa Rica and went on a zip-line tour of the rain forest canopy. It wasn't raining when we started out, but when we got up there, it was a torrential downpour. I didn't have a camera bag (wasn't allowed with the harness) and I couldn't protect the camera while zipping from tree to tree. I did have a plastic shower cap that I snagged from the hotel, but my camera still got soaked. It was so wet that the LCD screen fogged up from the inside. Maybe I was lucky but the camera never stopped working and still works great, almost 4 years later. It wasn't a pro body, just a mid level 20D.
Example 2: A few weeks ago I co-shot a two day wedding that was on a farm. It rained the entire time were were there. They moved all the activities into a tent/building but that wasn't good enough for the shots that we wanted to get. Eventually we told them to suck it up, we are shooting outside...rain or not. We all got a little wet, but I think we got some outstanding shots.