I tend to leave mine open all the time because I'm normally looking into something new or reading a new site I found. Its helpful because I may not want to read the whole article then or such but come back to it a few hours or maybe days later. I normally don't like to bookmark things because I tend not to use them efficiently. Like I'll bookmark something and then end up typing in the URL all the time or bookmark it and forget about it for several months so it ends up adding to my bookmark clutter.
The other reason I like leaving it open is because it provides the history(back button type) so if I find an interesting link off a site I can go back to the orginal site and see if it contains any other interesting links. Of course a large reason I end up doing stuff like this is because search engines are more or less worthless for looking for these types of things. I get better results finding one site I like and manually crawling all the other sites in the link web because they tend to be related when the topic is something like programming.
