http://en.wikipedia.org/wiki/Planned_Parenthood#FundingIn the fiscal year ending June 30, 2010, total revenue was $1.05 billion: clinic revenue totaling $320 million, government grants and reimbursements of $487 million, private contributions and bequests of $224 million, and other revenues $17 million. Approximately two-thirds of the revenue is put towards the provision of health services, while non-medical services such as sex education and public policy work make up another 16%; management expenses, fundraising, and international family planning programs account for most of the rest.
How do you know that private contributions aren't funding the ad buy? Would Planned Parenthood have no reason at all to oppose Romney in a world where the government didn't provide PP with any funding that could be cut? The obvious answer is that they would still oppose him because he might appoint justices to the Supreme Court that would overturn Roe v. Wade.