Kotaku reports that Steam has dropped all games from Insel Games after Valve learned the Maltese developer prompted employees to review its own games. They note a post on reddit showing an email from Insel CEO Patrick Streppel urging staff to review their recently released action/RPG Wild Buster: Heroes of Titan. They hear from Streppel who confirms the authenticity of the email and explains his position. He says they are appealing Valve's decision, and reassures anyone who already owns their games that they will continue to operate as before. Valve made the following post explaining their reasoning in this case:

It has been recently reported on Reddit that the publisher for this game, Insel Games Ltd., have been attempting to manipulate the user review score for their titles on Steam. We have investigated these claims, and have identified unacceptable behavior involving multiple Steam accounts controlled by the publisher of this game. The publisher appears to have used multiple Steam accounts to post positive reviews for their own games. This is a clear violation of our review policy and something we take very seriously.

For these reasons, we are ending our business relationship with Insel Games Ltd. and removing their games from our store. If you have previously purchased this game, it will remain accessible in your Steam library.