I've recently seen over 200K petition signatures requesting that Justin Bieber be deported, requests for Death Star Construction and the like. There have been about 140 petitions that have been given official responses. That is (at a minimum) 14 million signatures. Possibly 20 million if some were over-signed. This ONLY counts petitions responded to.
If you charge 5 cents per signature:
1) You will, in short order, have $1 million+
2) You will decrease the number of silly petitions you receive and the number of silly responses you must give.
3) You will have a financial record tracking the petitioner's name and political stand on the issue (you seem to like this sort of thing)
4) You will increase the value of the petitioner’s opinion from 2 cents worth to an entire nickel.