Greg Storey at airbag shared a couple of great examples. The real tragedy of RFP's is that they are all too common. I made a decision years ago to never, ever respond to these and I will tell you exactly why.
There are only three reasons to send out an RFP.
1) The company or person has no idea what they need and are looking for you to tell them. Lame.
2) They already have a firm in mind, but don't trust the bid so they would like you to spend a bunch of your time to help determine if it is a fare price. Totally lame.
3) They are going to make a decision based on price. Inexcusably lame.
Is there really any reason to respond to these?