Imperfections of personalized advertising

I am pretty excited about the possibilities of blending online and physical traces to deliver more relevant content and ads. So Kjartan and the guys at Unacast are chasing a huge opportunity for sure.

That being said, there are certainly smaller fish to fry - so to speak - first, because even the current cutting edge personalization engines (of the likes of Google) are so far from perfect.  I would even say they are totally broken. A few samples from the last two weeks:

• I was on a day trip to a city in the south of our country last week. On the airport I briefly checked if it made sense to rent a car instead of jump into a taxi or bus (I was picked up in the customer's Tesla in the end...). Since then, there have been ads for car rental in that particular city all over the Internet. 
• The last thing I bought on DX.com is shown me all the time, and the same applies to my last MPX.no purchase. Since I just bought these things, the ads are less relevant than ever.
• My Google Apps CRM shows up in ads for me all over the place, even if I am already using it daily.

As an engineer, I have no problem understanding that it is difficult to know what is (still) relevant for me. Some of the cases would require deep integration into ecommerce systems connected to ad platforms, and possibly raise additional privacy issues. But as it is, I would say that personalization in these cases make the ads less valuable than if they were not personalized. 

So before having my browsing of cars in the physical world affect the ads I see online, I would like to see the more basic problem fixed. Maybe the solution will come from the same provider (and I am sure it will be bought by Google) that cracks the "beacon code"?