I do think this is an increasing problem. I used to always be a 'one task' kind of guy, but now there's so much competing for your attention that it is getting increasingly hard to focus. We are now infinitely more contactable, by text, email, Facebook etc. so the chances that you'll get some sort of message while doing something else has gone up hugely.
(As I sit typing this I just got an email alert on my iPhone). I find that I lose concentration on what I'm watching on TV if I get a text message and have to start replying to it during the show. I think it's just going to take a bit more discipline, to finish one thing before starting the next.
I'm a lot more disciplined with Facebook etc. than when I first signed up a few years ago, where it wasn't uncommon to spend a couple of hours flitting between that and work. Now I check it once a day and only go back if somebody sends me something that urgently needs attention.
It does worry me a bit what the next generation who've grown up with all this will be like, as it would be kind of disastrous if they could never give any one task 100% attention as mentioned above. Even my younger friends still at university seem to really struggle to concentrate, and have to do crazy things like sleep overnight in the library, whereas I managed perfectly fine getting my work done in my house, even though there was internet/TV/Xbox/PS3 just a few metres away. It doesn't bode well for future world leaders...