I've been messing around with Sheldon Brown's Gear Ratio Calculator and it occurred to me that you could get the exact same gear ratios with a single 46 tooth chain ring and an 11-36 "MTB" cassette as you can with a 50-34 compact chainset and a 12-26 cassette. I understand why this isn't adequate for racer types, but this seems like a pretty good option for your average Fred's road bike. It would be lighter and one less thing to keep tuned and maintained. What with 10 and 11 speed cassettes available now you could even get pretty close ratios. Is there any reason not to do this? I wouldn't, but that's just because I'm a proper wimp and need lower gears than 34-26.