Has he ever had a prior history of just taking off? Has he ever even spoken of just leaving?
(ETA: I see from this pic that I found online it would appear he has a computer.)
Does he chat online or have a myspace page or a live journal account?
Or do emails? (if so someone needs to look in the sent folder of his email if it has not been deactivated.)
Has there been any activity on his credit cards or other bank cards?
Was the family expecting a new child?
Had any changes happened to his life recently? (within 6 months prior to his disappearance?)