"I think it is just sort of sticking it to her ... sort of twisting the knife a little bit," said Democrat Aimee Fountain, who decided to give $20.
It is tradition for Planned Parenthood to send thank-you cards to both donor and the people on whose behalf the donation was given.
The family planning provider denies having started the campaign, but reports receiving $800,000 nationally in the last few weeks.
"People are reacting the only way they know how, which is: How do I help protect healthcare services for women and how do I do it in a reaction that I regard as a threat?" said Planned Parenthood Vice President Deborah Ortiz.
The McCain-Palin campaign is not amused, saying: "This crass political stunt is yet another reminder that the Barack Obama campaign and its surrogates have given up on the 'new politics of hope' that they were so proud of a few short months ago."
The California Barack Obama campaign denies it had any involvement with the e-mail, saying individual citizens are responsible.
Conservative blogger Meredith Turney is appalled by the movement.
"This is a slap in the face of Governor Palin and the millions of women who have special-needs children, to ridicule Governor Palin for her making the choice, the courageous choice, I think, to raise a child with special needs," said Turney, Flashreport.org.
Turney also works for the Capitol Resources Institute, which just started accepting donations to fight for family issues and will also send thank-you cards to Governor Palin for her stance.
Planned Parenthood also benefitted from political backlash in 2001, when an L.A. Times columnist urged readers to donate to the organization on behalf of President Bush.