Update: Developer Matan Cohen got back to us with the following statement regarding the situation:
I am shocked by Valve's decision to ban my account.Original Story Below
It must be a terrible misunderstanding. Those "Fake" accounts belong to my family and to some close friends of mine. Last week they have joined Steam to support my project. It is not in any way a reason to ban me from Steam. I can't see the logic behind this ban.
For many days I was suffering from bullying on my own group of Art of Stealth. I have banned many members, and they revenged me by reporting to Valve on "fake" accounts. Valve believed them and removed my game from the store. Valve told me than my game would never be on the store again.
This is a very sad day for me. I was working on my game for 3 months and the bullies won.
The story regarding Matan Cohen's Art of Stealth took an unexpected turn this afternoon, with the game leaving the Steam store shelves. The act appears to have no relation to the developer's fight with critic Jim Sterling that we covered earlier today, but may hamper plans that he previously shared in talking with us to update it to be the best game possible.
The reason Art of Stealth is no longer for sale on Steam is that Valve has terminated their business relationship with Matan Cohen, stating that they have identified unacceptable behavior on his behalf. They claim that Cohen created multiple Steam accounts to give positive reviews to Art of Stealth, behavior that is in violation of their review policy, and that behavior is the reason for the removal of the game from Steam. For those who have already purchased the game, it remains accessible in your account as per normal on Steam.
This continues the somewhat similar path of Art of Stealth to developer Digital Homicide's titles, which were also removed from Steam earlier this year. The reason for that removal was very different: in that case, it was due to Digital Homicide pushing for information on users, but the end result is very similar.
For maximum clarity, we are going to include the Valve statement below: