Maybe it's a big problem for Microsoft, but for the rest of us, I don't really care if people can't type properly - the clients I want are clever enough to eventually work out they're not looking at the right web page.
It's not just mis-spellings but all the domain endings too... do we snap up the .co.uk, .net.uk, .org.uk, .com and the Twitter accounts and Facebook pages just in case?
No, we register our domain and our name and, unless we're Microsoft or Google or Yahoo, it's unlikely we're going to be targetted by the people who register alternative domains. Otherwise we spend money on rubbish, defending typos that very few people ever actually make.
Focus on your real domain name, publish it, add it to business cards and you'll lose very little business on typos in reality!