I see people commute like this but it's dangerous and may be illegal depending on where you are. You're right... it's hard for cars to see you... If they expect a bicyclist at all, they're certainly not expecting them from the left. All it takes is someone on the cell phone forgetting to head check before turning. As far as going up to the line, I only do it if it looks like there's enough space to do so. I'm not going to trouble myself only to get passed by the same cars just past the intersection, which can be tricky if it's a narrow road and annoying to drivers.

I guess my rule of thumb is to be as courteous as possible, especially since I'm sure I see many of the same drivers during my daily commute. If I'm predictable and polite, they will hopefully treat me the same.