To start: 16, 23, 24, and 46 are not mistakes HE made, but rather 'mistakes' other people made.
The first 'mistake' that is listed is not even Obama's fault. Chief Justice Roberts was at fault for the oath gaffe.
If he wants to nit pick about 19, then so shall I. The average words per sentence is about 15-20 words. To see how long it takes to say a 15 word sentence, I timed myself saying it at a normal pace. It took me 5 seconds. You can go ahead and try for yourself and if 5 seconds seems reasonable you can keep on reading. Divide the 1228 words by 15 words per sentence. Then multiply that by 5 seconds per sentence. Then divide that by 60 seconds per minute. That gives you 6.8 minutes. Not that long at all, hardly a 'mistake'.
As far as 51, I think we can all agree that is completely wrong, but it is my philosophy to give proof so check out the national debt clock. If 850 billion dollars quadrupled the deficit, it would have brought the deficit to 1.133 trillion dollars.
If these 52 'mistakes' do not make any sense, there may be a reason. One forum that was discussing the article had an interesting point. I can not find proof to back it up, but it is the first response: http://debatebothsides.com/showthread.php?t=76646.