I agree with that article in principle. However, it's quite flawed in a few areas. It mainly concerns petitions and their effects on 'real world' issues. Typically petitions don't have any bearing on such things.
However, online petitions can and do have an impact on mass media entertainment from time to time. Numerous television series have been brought back in some form or extended mainly due to online support (Serenity/Firefly and Futurama are two more recent examples). Such effects can be seen in gaming as well. For years online denizens called for a continuation of the Sam & Max series which happened in limited quantities last year.
Bear in mind as well that SE has shown regularly that they pay attention to the online postings of the playerbase. Numerous job changes have been lobbied for online and made it into the game down the line. While a petition may not have been specifically responsible, SE did in fact
significantly change their policies towards lost and stolen accounts.
Again, I agree that online petitions have little or no impact on social issues as noted in the Snopes article. They can and do have impacts from time to time in arenas such as this one. The cool thing, they're totally optional. If you don't think it's worth your time or energy then don't sign it or post about it.