A recent article I saw on the topic of helmets-- basically, yes, they are a target for cars. Statistically, people give riders less leeway when they see that they are wearing helmets (and more leeway if they think they are girls). Still, if it does come down to a crash, you're way better off with one than without.
In unrelated news, I'm in the process of sanding and repainting a BMX I found in a pile of trash a few weeks ago. I'm assuming it was stolen, as it looked like it was very hastily spraypainted black, and then abandoned when one of the tires went flat. I haven't had a bike in a while (I pretty much skateboard everywhere I go), but I think that this will be my new short-range winter transportation. I'm pretty excited. Any advice on bike detailing would be very much welcomed.