In this age of competition to attract sign-ups, logging in, and keeping visitors longer on websites, almost all dotcoms are using this “visual trick”. Go to yahoo mail and find the sign-in area. Go to gmail now and find where you have to put your login name and password. Go to Facebook and see where you have to put your login information. Go to any other website that requires login and password, and be amazed at the ease you can do so.
Then you get in, get updates, read emails, answer emails, give your status, download a few things, and keep thinking what to do next. In this whole process of online engagement, have you ever visually noticed the “sign out” button anywhere in the website? No way. You cannot, because sign-out button, almost in every case, is kept visually hidden. You need one extra step to find it and click out.
Does it really help to keep visitors surfing longer? We need to think on that. Since visuals always have one sort of appeal or another, hiding sign-out button might elongate our surfing time. I think it does not happen consciously, rather more on an unconscious line of thinking. What do you think?
khandoker's marketing blog 
it’s their business, who wants to get rid of the customer? Much time customer spend, much time they have the chance to make profit. From business point of view, i think its a good idea. From customer point of view, i think it is little boring, but not so bad.
I think, there should be similar and proper ‘ease’ in finding the both ‘sign-in’ and ‘sign out’ area. Because, as long as the visitors will find the websites useful to them, they’ll keep on visiting; but when they’ll need to sign-out, it should be easy to find the way to do so. When they need to search for the steps for long time, it becomes much disturbing and irritating! No one wants to waste their time in these types of activities. If once a member decides to sign out, he’ll keep trying to do so; here, the trick of the website to keep visitors searching for the sign-out process doesn’t make them satisfied or happy, rather it can keep them (visitors) away from opening another account in such site in the near future.