I agree that he should have known better than to check his laptop. However, he said in the video that he simply mixed up the two bags - one that he checked, the other that he carried on. I'm sure he's not the first person to make this mistake. He shouldn't be expected to pay for that mistake by losing his laptop - but that's what happened. Certainly, no one here thinks that his mistake is greater than the mistakes that are made daily by US in Philly when it comes to baggage handling.
We all know that there are some very airline-friendly limits on liability for lost luggage, so he is screwed, but that still doesn't make it right.
Coincidentally, there has been some discussion recently about whether pax should be REQUIRED to check their laptops - for security reasons. I doubt it will ever happen, but if it does, you can bet that airlines' the current liability limits will go way up under pressure from the floods of people who will certainly be in the same boat as this poor guy.