"What do you think is % of people that forgot "dot" after www?"
My educated guess, as I did look into this matter several months ago ... is that the percentage would be very, very low. Probably less than a fraction of Doberry's 1%.
So, while it may be worth it to register wwwsex.com (if you have a sex site), will you break the bank in this scenario, or could it be used as effectively with other words?? Extremely doubtful, in my opinion. Good Luck.