Why we get different ads for different Google accounts?

Do you know that Google is storing our personal search preferences and other sensitive information to display the most relevant ads when a web page is loaded?

Here’s a cool way to check it.
To get successful results, you’ll need a Google account which you have put searches regarding a specific area for a bit long time. If you are a computer geek like me, who’s searching for code segments, ORA errors or similar things throughout the day you’re an ideal person to check this

Here’s a good example I found recently.
I have two Google accounts and one used for most of my work related things. Most of the searches performed related to technical stuff done with this account. Here’s the advertisement (left side) I got in a website which loaded with this account.

Then I opened the same web page with Chrome connected to my other Google account, the Gossip one! See the difference

Google Ads are primarily filtered based on the content of the web site and the preferences of the user. You can check/modify the ads preferences by logging into Ads Preferences Manager. If you don't want ads to be personalized, you can Opt out the ad preferences. If you want to check which companies have enabled interest based ads on your browser and Opt out the preference, you can do it by visiting http://www.aboutads.info/choices/.

Check this video about Ads personalisation