I have occasionally thought about Ti bolts. My Cannondale is down to 17.8 lb and I'd be curious if I could get it to sub-17, without going to modern carbon fiber components. Ti bolts seem like the last resort though. Seems like drillium would come first. Reasoning being that replacing a given volume of steel with titanium would save less weight than replacing the same volume of aluminium with air.
Hmm, I just calculated that drilling 53 holes in the big chainring and 39 in the little chainring should save around 1.5 ounce. Gotta recheck that at home.
Ti bolts are considerably weaker than steel bolts. Carrying around the extra weight of the steel bolts will slow you down a lot less than having the face-plate of your stem snap off on a downhill.