Opera (my browser of choice) only recently introduced a “private” browsing feature. For if you don’t know, private browsing allows you to browse websites without leaving evidence of it on the PC. Firefox and Chrome have had this for a while.
Opera justifies the feature by using the example of being able to plan a surprise vacation without your other half knowing. But we all know it’s probably not vacation sites your trying to stop you partner finding out you’ve been looking at.
Having said, private browsing does allow you to do things you couldn’t do before with a browser—namely log into the same website with two different accounts at the same time.
I frequently use private browsing to access a different Gmail account without logging out of my usual one. Also, for my work, I have to access content via HTTP Auth with many different accounts, and the authenticated session lasts until you close the browser. Whilst previously I would have to use multiple different browsers, now I can open multiple private tabs to access the same HTTP Authenticated resource with different accounts.
So now you don’t need to feel so guilty about appreciating private browsing—there is a non-perverted purpose for it :)