Simple Letter or prehistoric cave drawing?

So today I was given the task of helping spread a branded campaign by signing up for a number of social media, video sharing, and blogging websites... 68 to be exact, and in doing so I found one common annoyance --- the verification box. They exist on a ton of websites to make sure that you are in fact a person creating a profile and not a computer program or some alien from outerspace who, according to the people who make these little puzzles, would not be intelligent enough to get around them. These boxes, besides being utterly annoying, are rediculous because in about half of the instances I had to use them, I myself could not even read the letters they put in the box, and while I am not the smartest man on earth, I can most definately read a letter. I even came across a few of them that, in addition to writing the words in the box, had to compute a math problem and give them the correct answer before my account could be 'verified.' I suppose its not a bad thing that people using these sites should at least be able to do basic mathematics, but again, still annoying. And finally, how are these words chosen? Sometimes the words that are put together are just too funny to think they are randomly generated?

These little boxes, however annoying they are, do presents an interesting opportunity for advertisers. Maybe instead of random words, company's could pay to have their brand names inserted instead? Why not? Just another 'arbitrary' thought...