Personally, I believe that the big problem with e-mails is, that you'll usually have to wait for a couple hours or days (depending how often said person checks their mail) to receive a reply and, even though it is inapplicable for business deals and the likes, for which e-mails are still more practical, it is quite comforting to know you're going to get a reply within the next few seconds or minutes, wouldn't you agree?
Also, how is TEXTING, as the word already implies, deviating from the written word? I mean I do understand that people tend to use linguistic shortcuts such as "lol", "hbu" and many many others but since that only happens in informal conversations?
Another thing that amazes me is that schools and parents blame their children for not writing properly whereas they should be the ones to teach them. Isn't that quite hypocritical? If you're a teacher and you can't teach your students, at least under the circumstances of them not being heavily dyslexic, how to read and write properly, wouldn't that imply that you failed them? Just throwing that in there.
Also it most certainly is not true that people are becoming less social, since where there used to be phone calls, now applications like Skype and MSN (which features calls) are more popular than ever and a lot of people do like to call or video chat. I believe it simply broadens our variety of socializing. After all I've got a lot of IMs and texts with friends asking me to meet them in town, go to the movies, etc.
It is so stereotypical for people to just put the blame on facebook, texting and IMs to cover up their fear of change and though change might not always be good, the world surely isn't supposed to stay the same forever on.
Edit: About the thing with not being able to write with your hands. Don't you have to write your essays by hand? Or written tests at school? I know I do, and though I have horrible handwriting I don't see how it is possible to lose an ability you get drilled into your head the many many years of being in school.