Back in the mid-90's, a fair number of computer game manufacturers used a method vaguely similar to this to copy-protect their games. What it would do is say "Type in the third word in the first sentence of the second paragraph on page 15 of the manual." There was a NASCAR computer game which prompted you with a picture and asked you to identify which track it was (again, using the manual).
The problem with this, and other methods, is that they are vulnerable to brute force. Assume you have a 50 page manual. Assume that there are 400 words on each page. This gives you 20,000 possibilities, which seems like a lot, until you realize that a 28.8k modem can send about 40 TCP/IP packets per second (no compression, full headers). So in just over 8 minutes, it's even money that just knowing ONE possible answer will yield the correct choice. Now, expand that to the speed of a T1 connection, and we're talking seconds, not minutes, to insert a piece of data into the network.
And this assumes that there are 20,000 possible responses for each question! It also assumes that you only know the answer to one question, and not most or all of them. Presumably lists of standard questions would be published and made available for download (with the answers) so that freenet node admins could just drop in a file or two and not have to come up with a few dozen questions each. Even if this functionality wasn't explicitly made available, people would write utilities to make it this easy... which means that how fast you get into freenet becomes a matter of how many such lists you have.
And therein lies the problem with "Think Cash"... unless the questions are rotated regularily, have a high amount of entropy in the answers, and a sufficiently large pool of questions, anyone can automate stuffing the freenet network with useless data.
That aside, there's another problem - this is a client-side security model! For sending data server-to-server, this model simply cannot work. There's too much data, and for the network to respond quickly to surges in download requests of particular pieces of data, it needs to be able to propagate that data without human intervention. This brings back the problem of the rogue server... and anyone serious about crashing freenet would opt for this, instead of messing around with client-based insertions.
Just some food for thought...
Society needs therapy. It's having
trouble accepting itself.