I post a question, and wait for answers. I create another account and answer it. I pick my own answer as the best answer, and I lose no money. I gain the information that others gave me for free.
This. When it comes to money, people will exploit it as much as possible.
From their FAQ: "Do I have to pick the winner of my contest?
If your contest receives less than 5 entries by the time it ends, you're not obligated to pick a winner. You have the option to extend the contest for seven (7) days for free. 'Extend Contest' and 'Contact us' link information is available on the contest page.
So, what if I just forget to log back in and award people the prize? Does google automatically pick a winner?
Yes, google will automatically pick a winner, as explained here in the faq (http://prizes.org/faq)
How does Voting work?
You may vote on as many contests as you wish. However, you can only vote for one entry in a given contest each day, and you may not vote for yourself. You do have the option to vote for more entries in the same contest tomorrow! If buyers don't pick a winner when the contest ends, winners will be chosen by popular vote.
Maybe they tolerate that behaviour as long as not everyone is doing it. There's probably some automatic way of detecting people cheating the system and suspending the accounts automatically.
I'm mostly concerned about the opposite. I can see an answer having 200 replies and none of them being more deep than an online search.
All the time.
It will be like yahoo answers with money. train wreak waiting to happen.
I assure you the best answers I gave/got at stack overflow and some other content specific forum was not because I/they needed $5 to help somebody else.
I post a question, and wait for answers. I create another account and answer it. I pick my own answer as the best answer, and I lose no money. I gain the information that others gave me for free.