right now I would not worry about it too much, their profiling is so horridly wrong its embarrassing, I search for motherboards I get ad's for toasters, I delete some spam and I get ad's for mail order Russian brides, I search for some religious information, I get ad's for penticostal material and Scientology though religiously I consider myself pretty conservative (raised bouncing between Lutheran, Catholic and Presbyterian)
It seems to be a average of crap and a dumb guess based on stuff they happen to see you do, and with wandering minds its damn near useless, though I do get ad's from computer retailers like a day or two after seeing the specials the ad's are boasting about which is really pointless.
everything they collect seems to be wrong, and frankly its an artificial bubble, putting great worth on snake oil and I can not wait for it to burst ... it wont be too much longer IMO (ie decade). They have no real clue, their data is flawed, the only people really dumb enough to fall for it all are the ones writing the checks, and they will be hurt. Unlike the housing and auto industries*, Google is not too big to fail and your usuall standby's that have been around before google will be there in the long run.
*BS: It would hurt bigtime, but clearing out dead wood is a good thing in the long term (and I personally would not wipe my ass on a GM product, though I just designed their 2014 corvette maplight PCB ... sigh)