If we're bothered by Google not suggesting fun things to stumble across based on our previous searches and visited sites, here's a possible suggestion: the algorithm could be tweaked to include an element that looks to see whether you've made your searches etc in work time – the middle of the day – or in the evenings. I find myself making very boring searches at work; and look for entirely different things when I'm trying to enjoy myself. Just a thought :)

It's a niceidea, but you must specify your working times... Some people works at night, or has informal times...
Maybe an easier solution will be a "I like it" button, so Google can gather information about your preferences...
It's a fragile balance between information and personal information.