According to the study that took place in London, only one of six shops surveyed actually repaired the problems created. The rest overcharged or misdiagnosed the problem, as well as some shops who went pouring through the contents of the machines' hard drive. The worst of them was actually caught pilfering passwords for various online accounts, ranging from emails and eBay to online bank accounts. The article undoubtedly raises the question of how widespread corrupt repair shops are.
Studies and results like this are not rare. Last year, there was another survey that showed similar repair shop horror stories. Though there's not much we can do about it, it's nice to know that there is plenty of room for quality work – so if you know a tech who does a good job, toss them a thanks. There are plenty of good techs out there, and unscrupulous ones only make it harder for them.