The Number of the Doctor

Are you as confused as I am about all this business of Matt Smith being the 13th Doctor?
First of all, let me say that I don't participate in any on-line forums. That way madness lies. There are some corners of the internet that have bred the most terrible things... etc.
I therefore don't know what others have to say on the matter. All I know is that Moffat says he's the 13th Doctor, and the regeneration limit will be broached (and breached) in the Christmas Special.
Of course, semantics will come into it. 13th incarnation of the Doctor, or there have been 12 regenerations? If the latter, then the regenerations have indeed been used up and the Doctor doesn't have any more. Not content with having the 50th anniversary land on his watch, and sorting out the Time War, Moffat is determined to crack the regenerations limit debate as well. (Mind you, he has left the hunt for Gallifrey and the potential for a female / ethnic minority Doctor for future showrunners).
As for the number of Doctors there have been, the answer is - indubitably - 12. Smith is the 12th. John Hurt became the 9th and moved his successors along one place. (Don't bother with the Brain of Morbius thing - that's been well and truly put to bed).
How many regenerations have there been? 12 also.
1. Hartnell to Troughton. 2. Troughton to Pertwee. 3. Pertwee to Baker T. 4. Baker T to Davison. 5. Davison to Baker C. 6. Baker C to McCoy. 7. McCoy to McGann. 8. McGann to Hurt. 9. Hurt to Eccleston. 10. Eccleston to Tennant. 11. Tennant to 10.5. 12. Tennant to Smith...
Yes, the only way this works is that Tennant used up two regenerations. Personally I would never have counted the creation of 10.5. The Doctor stopped the regeneration, siphoning off the energy into his hand, creating the half human version of himself. So not a regeneration, in my view.
Whatever way you look at it, it means that Moffat is wrong and that Smith is still only the 12th Doctor - but he doesn't have any more regenerations left, so does indeed become the last under the old Gallifreyan rules. (It also means that the Valeyard comes into being between Smith and Capaldi).