After reading all the responses, esp from genec and joejack951, I'm going to rethink this and put myself on-the-fence on this.

I think that theoretically, sharing the road is a great idea. Everyone belongs. A very nice concept indeed.

But, realistically, it's very much too touchy-feely for many people, and it's going to take a LOT of something to make this work. I'd think somewhere along the lines with....inundate the public with facts about the realities of streets...No, streets are NOT just for cars; YES, cars kill; YES, too many cars are the reason for so much congestion, etc. And then explain the shared-lane concept = sharrow, meaning that cars MUST yield to bikers, pass them on the left, and YES, the bikers can use the left lane to make left-hand-turns.

Then, enforcement...including if the sharrow doesn't work, i.e., bikers are still getting hit and drivers are otherwise making it difficult to ride on the streets, then, the entire sharrow-lane turns into a bike-only lane, with bikers able to use the traffic lane as well (left-hand-turns). This will (hopefully) get drivers to take this sharing seriously, pay attention to bikers, and to think twice about cutting off bikers or otherwise making it no-less-better than it was before the sharrow.

And, reality is, there's probably no city anywhere (in the US, anyways) with the chutzpah to give up an entire lane to bicyclists, and for this reason I realize completely that this underlying threat is kinda...dreamy, to say the least.

It's a word for "Shared Lane Marking", or "Shared Lane Arrow".

Have a link:

http://www.bicycle.sfgov.org/site/dptbike_index.asp?id=28372

As members have already posted, sharrows are generally preferred to the design of most bike lanes.

Question: would they be more effective if they were painted bright yellow?

That makes a lot of sense, hopefully they become common in other places, I know a few streets here in Toronto (ON, CA) that could use them.

Can some Highway Department type tell me how much Sharrows cost per mile or whatever vs bike lane markings? If a white stripe and a bike logo once a block is cheaper than sharrows guess what the City Fathers will want.

Can some Highway Department type tell me how much Sharrows cost per mile or whatever vs bike lane markings? If a white stripe and a bike logo once a block is cheaper than sharrows guess what the City Fathers will want.
Not the point. Sharrows work where there isn't enough room for a bike lane, without reducing the number of travel lanes for MVs.

Can some Highway Department type tell me how much Sharrows cost per mile or whatever vs bike lane markings?

Good question / point. The cost is exactly what the people who make the decisions will look at.

Let's do some math.

Bike lane stripe = ~4" wide, continuous stripe except for intersections (say 100' every 1/2 mile) = 1690 ft^2 of paint per mile

Sharrow the size of a parked car = 7' x 14' (close enough :)) = 98 ft^2 per sharrow or at the equivalent paint use of a bike lane stripe = 17 sharrows per mile (a lot of sharrows in a mile)

By that estimation, the sharrow wins as I doubt they'd paint that many sharrows. The downside of the sharrow is the need for a very large stencil and the greater maintenance necessitated by increased wear (although it woouldn't be any worse than directional arrows that are already painted on roads). Bike lane strips use existing equipment to lay the stripe but then need a small stencil for the little bike guy. They also require street sweeping to remain clear of debris. I'm going with the sharrow being hands down the cheaper option.