I think that the death bell for government raids of MMJ petitioners is in the final stages. Pretty soon it should be mostly legal, people like Barney Frank are pushing it in Washington, and he is just one of many. They may be too afraid to just outright pass it because of the religious votes, but it is inevitable.
If nothing else, by posting this you are basically admitting that you are not some kind of MJ kingpin, so you should be fine to sign it. If nothing else do you really think that the government has the resources to hunt down the tens of thousands of people that sign a petition for mj get warrants and bust your shit up?
No sense in worrying about this, if you are not a legit patient you should be enjoying what you like to enjoy, and if you are a patient fuck em.