How often do you experience the "internet coma"?

So often, I find myself here, or on facebook, or watching videos on youtube, etc… then I look up and realize exactly how long I’ve been on the computer.

It seems like I’ve lost time. For example, I logged in here at 9:30, planning to leave a few comments and log out. I’ve been on for just over 30 minutes now.

I’ve lost two hours on youtube several times.

How often do you do this, where you plan to log in “just for a minute” then you realize you’ve been online for much longer than you intended?