It's a very big problem. I've just had to sack our last IT support provider due to ongoing lack of errr... IT support. We employed them to free me up for other things. Even then, I constantly found myself doing what they should have been doing (system updates, checking error logs etc). I dread to think what state our systems would have been in had I not been an 'enlightened' customer. God help their existing clients!
Many IT support companies have shot themselves in the foot over many years and in doing so have also given good, attentive support companies a bad name. Office 365 and Google Apps was waiting to happen to them. The good IT firms are now providing value added services and are able to hold onto much of their client base, as they have treated them well over the years and are seen as trusted partners. The bad guys better hurry up and retrain!