not that I'm aware of. It's a system wide message designed to keep you informed as the who has favor, etc so I don't believe there is a way to get rid of it short of removing the chat window from your interface.
There are things like that, the you have been playing for x hours message, a new build of guild wars is available type of messages that can not be removed.
Useless, but necessary I guess...
Technically those messages are not spam, the only one that would really be called spam is the "new build of guild wars is available" that shows up every 5 seconds when there is a new build. But as those are in green they are system messages and cannot be disabled.
