Getting here bit late on your post but wanted to let you know that I have a 2007 Cobalt LT Sedan, 2.2 - 4 cylinder, bought new Jan. 22, 2007 . Had 15 miles on it (8 of which we put on during test drive) when we pulled off lot. Has been a fairly decent car up until the recall on the power steering motor.
When I took it in for that replacement, I had mentioned that recently there was a small clunk from front end, going over even the smallest of bumps, which seems to be progressing to a bigger clunk in last few weeks, sounds like whole front end going to fall off and asked if they could confirm if the lower front control arms were going bad. (Thanks to forums like this, I didnt look like a total fool and actually acted like I knew what I was talking about ). It took approximately 10 seconds for a guy on the ground looking at each side for them to say, YES they are almost on the ground, and need to be replaced.
Well, I am out of my warranty by 5 months, and the kicker is I only have 13725 miles on car !! So to answer your question, yes these parts can fail at moments notice. I am so upset right now that with mileage like I have, I am already faced with putting money into this car. What can I expect in the next 13k miles to have to replace? I have learned my lesson, and will now make sure to let anyone who wants to listen to not buy a GM vehicle. Our old '01 Impala (bought with 7500 miles on it in 2001) was nothing but a headache, and now same with this vehicle.