I think this idea sucks, and it will hurt commerce in area. We live in Seattle, close to the Montlake exit on 520, so we frequntly jump across to Bellevue/Redmond to shop and eat. I would certainly consider taking my business elsewhere along the I-5 corridor if it was going to cost me $12 to get to the east side.
On top of that, late at night on the 520 bridge deck is one of my favorite places to....errrrrrrr.......drive it like I stole it......
