The point of the sharrows is "basically to indicate to motorists that they should beware for cyclists," says city project manager Kyle Chisek. They smaller circles with bikes in them that have existed on Portland's streets for years are "wayfinding" markers for cyclists, these are to alert cars that they're driving on a road with a lot of bikes. Exactly 2,100 of the big white arrows are being installed on 53 miles of existing bike routes around inner Portland (though not in some places that could really use 'em, like Couch) as part of a $483,000 project funded with federal stimulus dollars. Each sharrow costs $229, with installation costs.
So are the sharrows a cheap way to make big changes or an expensive way to do nothing? They're not adding any new bike routes and, of course, I like to see big changes (involving cement! Not just paint!) that make problem biking areas much safer. But the sea of sharrows should make existing bike routes safer and more pleasant to ride on and I think it's a good idea to get our existing network safe and strong before branching out to new routes over the next decade... especially when the feds are willing to foot the bill.
And personally, I have more people who shout at me when I'm biking on places like SE Ankeny than on less-traveled routes. Especially on weekends, people from the suburbs or out of town try to zoom up the street and seem shocked and appalled to find so many cyclists in their way. I welcome a big white arrow in the road that says, "Hey doofus! You're on a bike route!"