Here’s a quick tip.
It appears that Criteo provides personalised ads in Facebook which can end up pestering you about specific items you may have been browsing on the web. Personally, I had been looking at 32GB G.Skill DD3 2400MHz on NewEgg and an ad appeared for the same product in Facebook.
Fortunately, you can opt out specifically of Criteo by visiting http://www.criteo.com/us/privacy-policy and turning the opt-out on at the bottom left of the screen.
That should at least stop personalised ads from Criteo from coming through.