I have an app that I bought, unfortunately the company was also bought and the new version is seriously worse.
Hiding is not possible for third party software. Removing MAS receipt makes the software "damaged". Setting softwareupdate ignore cobook, does not work either.
There has to be some hack available, I don't want to "update" by mistake, and it bugs me to see the red "1", since I usually keep my software updated.
This would however be a downdate.