Obligated and obliged don't have entirely the same meaning though. Here's a quote from a certain forumite
using 'obliged' in a way which, IMO, could not be expressed with obligated.
Last Sunday, a bloke in a Beamer started encroaching on my right of way and looked decidedly pissed off when I continued and obliged him to stop. He then had to drive round three sides of a rough rectangle and round a roundabout to get where he was going, whereas the cycle path I was on cut straight across. It was delightful to meet him again at the far side and get onto the cyclist-priority crossing just before he reached it.
To my mind, where obliged has the sense of 'physically forced', as there, it can't be replaced with obligated. Obligated expresses a sense of obliged which is more like 'bureaucratically compelled'. Whether it's worth having a slightly ugly word to express that particular sense of 'obliged', I'm not sure, but it is distinct.