If we're talking about the first leaked version of PRISM, we still don't even know if it exists or how it works. Subsequent revisions have made it seem that if the NSA doesn't have the immediate ability to query the companies' backends, then they have some kind of carte blanche ability to ask for data and immediately receive it. If either of these are true, then certainly, where are the whistleblowers? If not, and there's a very real chance that neither of these are true, then the question doesn't make sense.
If instead we're talking about FISA orders, there's nothing secret to blow the whistle on. Everyone knew what they would allow. Congress was briefed on what they actually have allowed. The EFF has been in court for years (7 and 5 on different cases) to try to just figure out if their clients have standing to sue over FISA. Many of the companies on that PRISM list now have transparency reports that tell you exactly how they disclose data and provide numbers for requests (other than FISA, which you're not allowed to do). There's been tech blog coverage for years by sites like Ars Technica that discuss everything from the flawed ECPA to the attempts by the Obama administration to use national security as a guise to subvert all attempts to find out what these intelligence programs even do, let alone who they do them to. So, what did you expect them to blow a whistle on?
For instance, Google and Microsoft are both now reporting ranges of the NSLs they receive; in effect, a kind of whistleblowing, albeit a legal and vetted one. NSLs are very much like FISA orders, in that they contain gag orders and have minimal oversight (and no public oversight) for their approval. Where's the indignation and action over those?
If we're going for hindsight here, the real question is where the hell were the major news outlets and where the hell were the American people? Or why has Congress been willing to approve this program on multiple occasions? Assuming incompetence in all three of those groups, the usual response to those questions, is not an acceptable answer.
If instead we're actually looking to the future, we need to ask how we're going to hold the Obama administration and Congress's feet to the fire to make sure that this ends, and that any real search beyond basic information (in a very narrow scope!) requires probable cause demonstrated before a judge, and that notification of a warrant can't be gag-ordered and withheld indefinitely.