My main commuter bike is a 2010 Cannondale Quick CX. As a commuter bike, it's great - it's not too heavy, not so expensive or trendy that it's a huge theft risk, fun to ride and reliable, except for the fact that bits keep falling off it.
The problem is plastic. They got the weight of the bike down by using plastic stuff where ever possible, which is fine, except that every so often I'll look down while I'm riding and discover some plastic thingy has vanished completely or is dangling.
Yesterday, with 10 miles to go to get home, it was my chainring guard. I was pedaling like crazy into a headwind (and going nowhere fast), when something just didn't sound right. Sure enough, I looked down and the guard was flapping around the pedal.
I managed to work the guard off and then rode the rest of the way home with it dangling off my handlebar. Since the bike's still in warranty for another month, I'll take it to the shop and have them fix it.
I probably don't need the guard, but it is nice to have since the guardless chainring on my race bike has drawn blood more than once. I have scars on my right calf from that thing stabbing me when I least expect it.