Yes, indeed. And there was even a series of photographs of one such attack by kids in front of a Moscow hotel, where an American tourist, probably in his early thirties and quite large and fit-looking, was being surrounded, gripped from all sides, and nobody on the street, within camera range, did any damn thing at all whilst he was losing everything.
But the problems are far removed from the street, too. Marbella had a series of 'forced' sales of villas to various hardmen; Rod Stuart quit and so did 007... all people that can or could afford security. It isn't worth the risk. Even here, at a building next to me, I remember watching as two policemen escorted away a pair of gents from eastern Europe who had gained access to an apartment where they'd stored stolen goods. But on the basic level, the gypsies are the more visible problem with their flower sellers who distract you with a babe at the breast whilst offering you a flower you are supposed to buy as another of them works behind you... Fortunately, they are very easy to recognize. If you are aware of the scam. With many thousands of virgin tourist a year...
Had a slight run-in with one just a couple of weeks ago, when I had the mad urge to try street pics. Not only did I get to see the older lady with the cantilevered front, but also this woman, working with her male partner. He was making elaborate sandcastles on the beach which were rather cleverly done, and I stopped to take a pic as he was doing it; the woman, who was obviously in charge of the hat, called something out to him which he ignored. I took my shot and continued along the pavement past her, and got a mouthfull of abuse when all I did was tell her they were rather nice... obviously, she wanted money. Nice PR. She got zilch except for a sore throat.
The irony is, they are all doing this sandcastle thing illegally, in broad daylight, and nothing ever gets done about it.