Social media sites are not refuges for failing fundraising programs. If you're failing in the mail or email, you won't make it up in Facebook. And if you're not getting any action now in Facebook, don't think Pinterest will solve your problems.
If you aren't successfully raising funds through email, postal mail, telephone, or any other medium, the problem is not likely the media. It's what you're doing with them. You are failing to connect your cause with people, and there never was and never will be a communications medium that solves that problem for you.