Microsoft, like most companies who run an app store, on occasion has problems with fake or malicious apps. You know, the ones that purport to be official, but charge you money upfront without a trial, something even more egregious for already free services.
I have seen a lot of teeth gnashing over this and lots of "look at THIS example!" posts. Even Microsoft has recently chimed in to say they are going to be doing more. But you play a role too.