The Bitcoin Foundation represents no-one but it's members.

By signing the petition, non-members are lending credibility to the Foundation by implictly recognising it. That might not be a great idea, considering it's recent history.

As a non-member, I do not intend to interfere with the internal workings of the Foundation.

I would however sign a petition asking the Foundation to act with integrity and to stop pretending they represent the 'Bitcoin community'.