I think that should be mandatory to have the platforms tags.
I have a PS3, Xbox 360, Wii and Ipod Touch but I never play anything on PC.
I started adding tags to my ignored and interesting tags, then I began to notice a lot of tags like:
eve-online, lotro, wow, etc without the platform.
It is just impossible to add all the PC games to the ignored tags.
Also, I bought a Wii just to play Mario Galaxy games, so I would like to ignore it for now and focus on PS3 for example, but if the questions aren't tagged with any platform I can't filter by Interesting/Ignored, so this filter becomes useless.