This. My favorite is when I search for products on a website or app and the results appear in batches, with subsequent results interleaving with the previous results. So when you want to select a particular result and start to move your mouse and click, or move your finger and press, you often end up selecting something unintended because a later result pops into the location.
I do this in the gmail mobile app all the time thanks to their ads injecting themselves in between the emails several seconds late. They must love me, their most engaged ad consumer.
Handy tip: If you disable all the tab category things in settings and go down to a single category (Primary), it will stop showing you ads entirely.
<sarc/> A website can track where your mouse pointer is, but surely they wouldn't do this on purpose just to get ad revenue.