Mentioned earlier about individuals (or groups) in music who come up the traditional way, ie. work the small clubs, build an audience etc. become hardened, Liam skipped this process via the Cowell vehicle.
Of course the traditional route doesn't make you immune to issues (as was pointed out with Oasis and drugs being mentioned), but it does give you a better chance at taking the crap that inevitably comes your way.
Propelled by the immense leg up that is Idol, X Factor, Got Talent, its instant fame/success, as opposed to having to slowly grind your way to success, and being given a solid grounding while doing so. Sting talked about driving up and down the motorway in a van being in The Police, playing gigs (sometimes to tiny audiences), struggling to get a record deal. This gives you a perspective that these talent show winners/successes don't get. They get instant fame, and in Liam's case immense fame, but what happens when this ends as it usually does in these quick fire successful acts? There is no safety buffer for him, no memory bank of playing infront of 30 people at a gig and then driving 80 mile to another gig to play infront of another handful. He has only known massive crowds, flashbulbs going off, paparazzi etc.
The two Simons created shows that transformed music and television, but if you have the talent to succeed I'd be looking at the traditional/organic route.