If those fans go out major overheating can follow. Don't know about laptops but I know from coin-op that those countertop machines that get placed on the bar at your local hangout tend to freeze up when fans go dead. Those fans are about $4-5 bucks at the most, and only a couple of wires to hook up and 2-4 screws depending on if they have screws on all the corners. Easy fix on those but I've never had a laptop apart. Same fans I see in my computer tower as I type this.
The fans we dust out, you have to stick a key or end of a paperclip or something in the fan blade, so when the compressed air hits it the bearing/plastic housing meet doesn't melt from the excessive speed the forced air places on the blade..