I guess what surprises me the most is that I'd have thought the biggest problem with having 20 tabs open is... you have 20 tabs open. Are you seriously reading all those websites at the one time? If so, then you must have the worst case of ADHD I've ever come across! Please, get some help :-)
I work in technical support for an eCommerce company. I have two FF browser windows open with 5-8 tabs in each one (minimum). I manage whatever issues I'm working on plus look up other sites to assist the lower level techs with their questions, too. Sometimes I'll need to test email functionality, so I'd open GMail, Yahoo Mail and Hotmail all at once. So, yes, there are real reasons to open multiple tabs (I also have Opera and Safari installed, too, for those rare instances where I need to test those browsers, too).