Since an e-petition site like the one linked gives people opposed to an issue the impression that they've accomplished something, those people are that much less likely to do something substantive to resolve the issue they're concerned about [Citation_Needed -- I couldn't be bothered to find it].
So, less is actually done to oppose the issue than if the site never existed in the first place. It actually helps those who are in favour of the issue opposed.
E-petitions aren't useless: They're worse than useless.
Since an e-petition site like the one linked gives people opposed to an issue the impression that they've accomplished something, those people are that much less likely to do something substantive to resolve the issue they're concerned about [Citation_Needed -- I couldn't be bothered to find it].
So, less is actually done to oppose the issue than if the site never existed in the first place. It actually helps those who are in favour of the issue opposed.
E-petitions aren't useless: They're worse than useless.