Pettigrew's indebtedness to Harry

[Darlene]

No: HPFGUIDX 30324

All this talk of the Shrieking Shack had me remembering something.  
Dumbledore tells Harry in the end of PoA that Pettigrew will be 
indebted to him, because he saved his life.  {Remember, Harry is 
concerned about Trelawny's prediction, and is worried he has helped 
Voldemort (which proves to be a founded concern) return to power? } 

So, is Pettigrew just the ultimate slimeball (or, in his case, the 
ultimate follower) that doesn't follow rules of the game?  Voldemort 
follows them in his own twisted way (like making Harry bow).  Makes 
sense, but I was just wondering if anyone else wondered this.

Thanks!

Darlene