Intrusive Advertising?

Recently I've noticed that products I search for on Google, happen to show up in Ad spaces on various websites, placed there by Google Ads. In one case there was a long-board I was looking to buy that I had researched using Google, and for a whole month it would appear on almost every website I visited as a Google Ad. These Ads are present because of Google saving my form data on my computer, or possibly even the searches themselves. I can understand their approach, by placing the products that I search for in front of me constantly, greater increases my chances of clicking their Ads and buying the product. However is it okay that they remember what products I buy, and is there a chance they may also be saving all of my searches to gear their Ad spaces to fit my personality? For example I was looking up basketball stats, between Lebron James and Michael Jordan, as well as some new basketball shoes, three of which appeared the next day in this ad below. Is it possible they will create a marketing scheme personalized towards me, and constantly barrage me with basketball shoes and products?

Although this may be a creative form of effective advertising, I can't help but think it is a slight invasion of privacy.

Which raises the question, what is the limit to which companies can find customer research to create effective advertising?