I don't have Facebook - it's too intrusive for my liking.
I've posted the following before but thought id repost it just in case anyone is interested 
You can easily turn off Googles interest-based ads. Then you won't get weird targeted ads turning up on mumsnet sidebar or on other sites.
OPT OUT HERE. You may have to reset it each time you clear your cookies.
If you use an ipad or iphone with ios7 you can also TURN ON 'Limit Ad Tracking'
Settings>>Privacy>>>>Advertising>>. Toggle Limit Ad Tracking On
You can also turn off location based ad's if you use ios7 (this will stop Apple tracking where you are and using the info to send you spammy ad's from nearby businesses.
Settings>>>>Privacy>>>>location services >>>>(scroll right down to the bottom of the page)) system services >>> then TOGGLE OFF 'Location-based iAds.
HERE is more info about how to opt out of interest based advertising on other search engines and twitter etc.