How old are you? This seems like a relatively naive worldview, because it doesn't take into account how crafty people can be. What if I transfer some money to you and then claim that you did it by impersonating me? There would be no provenance of what you could be capable of doing since all info is public. Of course if you'd rather keep your age to yourself that's fine, since we're not in that theoretical society now.

You can absolutely kill someone without preparation, especially when emotionally or politically motivated (out in public with a strong punch, elsewhere when the opportunity arises). Check out this page on wikipedia for some material: https://en.wikipedia.org/wiki/Crime_of_passion

In a better world, ads would exist to do that. However as it is, they exist to push the viewer in any way possible to buy the product. If you see something in an ad, it means that the company marketing it has enough budget taken out of manufacturing and R&D to pay for the ad. So the vast majority of the time, if you see something in an ad it means the product is not that great. (edit: Because good products don't tend to need ads as they speak for themselves and their existence travels by word-of-mouth. Also called "organic traffic" by SEO people)