I'm one of those people who regularly runs 10-15 (sometimes more) browser tabs at any one time, only realising how much memory is being used when the fans kick in and various parts of the machine start grinding to a halt or slow responses.
For work, I permanently have at least 4 tabs open in Chrome with the basic web tools, then other programmes like Outlook, Skype and Evernote. Skype, Outlook and Chrome can all be quite memory intensive, the latter especially, when you have a lot of tabs open.
I recently found a little Chrome addon called Tab Suspender through an Engadget list. It's done wonders so far. It actively suspends a tab and re-opens when you click on to it. My fans haven't kicked in thus far and the laptop is responsive. Small things, big differences.
Before Tab Suspender: 80% RAM usage by end of day
After Tab Suspender: 15% RAM usage by end of day
Go check it out!