I've heard that polishing the Ti part actually reduces it's strength, as the microscopic scratches weaken the Ti. I have no idea if that's true. All the Ti bolts I've got are polished. I understand it makes good medical metal because it's pretty hypo-allergenic or something.

I would think a blued bolt, while highly possible and not all that hard to produce, would still rust due to sweat. I'd love to have black bolts that wouldn't rust in a lot of places on my bikes.

Some bolts are simply the right size to be purchased in Ti from a fastener vendor, and many others aren't. I get all my bottle cage bolts that way, either in black steel or Ti.

+1 with Dirtdrop, and I think kpug105 can relate. I bought a Ti frame and added Ti stem bolts, brake shoes, axles, bottle cage bolts, seatpost binder bolts, chain rings, 2/3 of the rear cogs, etc. I went overboard on that thing and darn near bought Ti spindles for the Look pedals, too. A lot of money, and I didn't notice any change other than psychological. There sure was a lot less "change" in my pockets....