When I was 10, the way I used to think of it is this:
I had noticed lots of reasons why Santa (Or Father Christmas as I knew him as a child) was not the one delivering my presents: For instance I knew that we had no Chimney, and the parcel would have my mums handwriting on it etc... However I hadnt really developed the ability (Or you might say the weakness) to correlate the evidence against Santa that was before my eyes - I didnt really see any reason to not think he was real, especially when I didnt LIKE the idea that he wasnt real - were was the fun in that?!
As an adult I still dont have a problem with Santa being real - He is the spirit that represents the holidays, therefore he has spirit like powers (Walking through walls and being able to forge my mums signature). I mean really, if your going to beleive in Aliens, Bigfoot and Health Care reform who am I to judge?