That's called a captcha, and i have no idea if they use one here now, and if not, why not. As for Fresco's question, yes there are indeed people who will promulgate and disseminate spam for clients. The process is often automated, which is why a time limit has been imposed on posting--to eliminate much of the automated spam. Of course, it's a war, so the other side will certainly learn to deal with such obstacles, and probably sooner rather than later.
Several years ago, and in the month of May, we began to see "bots" arriving here. There were very obvious telltale signs of the "botdom" of those signing up, which i have never openly enumerated--i don't want to give the jokers doing this any clues. I may get in trouble fo saying this, but i believe that the member calling "herself" selectmytutor is a bot, or rather, a programmer attempting to perfect what can be called a content bot. Long after "she" registered, "she" added a profile in which "she" claims that her name is Leesa Johnson, and "she" has added a picture of a young woman with European features. Such an image can be found, of course, at any site providing clip art. The name can come from a name generator. The potential of name generators has been exhausted already. But if you are normally called Pandit Gullawar Prathachulthorn, you might do better with AdolfHunson from a name generator, for however implausible that name may be.
Content bots can be useful to those selling services who are more interested in probable success than volume. For example, someone would launch a couple of content bots, one which asks for kitchen fixture suppliers in Norfolk, and another which supplies the name of such a supplier. The original bot can cycle through a list of city names for the UK. Content bots also search the web for questions on a certain topic, and then dump their content where they find such questions. I should think you wouldn't make much money at that, though, because your response would not necessarily lead someone reading at that site to call His Lordyship's Gold-plated Loo Fixtures, Limited.
Another trait of content bots is mimicry. Apart from the implausible name, i first began to suspect "selectmytutor" of being a content bot because "she" would post at the end of a language learner's thread, parroting what another, actually human member had posted. When selectmytutor sets out to attempt an original response in English, the results are usually hilarious, and pathetic. That's why i think of selectmytutor as a long-term programming development project.
Here now, i've got other things to do. Maybe i'll comeback later with more comments. Maybe i'll go make myself a bacon sammich instead.