Many contractors hired on one freelance job, should you accept an offer?

On ODesk I recently posted a bid on a job, and got an offer from the client. I had asked for a small upfront payment, just to make sure the client has stakes in the fix price job. But the job offer sent by client was without any upfront payment.

I went back to the original job posting to see something, and I noticed that another contractor was already hired on the job. That contractor had a nice profile, so I started clicking around to get more information about the client. In his the client's past ODesk contracts, I found another job with same hiring pattern, only on a very large scale. The screen shot of the bizarre scenario with 8 people on one job is given below:

Over the weekend I stayed confused, tried my level best to resist the temptation, and finally accepted the job offer.
I sent a message to the client after accepting the job, and started work according to the specifications outlined in the job posting. It was about creating an Android app which would disconnect calls received from a list of numbers maintained by a community. It was a very simple task on older versions of Android but the latest ones don't let apps mess with telephone calls freely. I spent a full day on the job researching ways to make things work, I was also expecting an answer from the client and I got desperate by the end of day cause that's not the way it's supposed to be.
Have got a reasonable number of projects on my profile, and I believe clients serious about their work communicate frequently. But, I decided to wait and see until next day.
The next day I sent another message to the client, expressing the doubts I had about him. But he didn't talk back, and some time after mid-day I decided to end the contract.

Drop Scene:
Later that day, the client sent me a message through ODesk saying that I had already spent several hours on the job and I should not end the contract as my work would be wasted this way.
But, I had taken time before cutting the cord and I had a gut feeling that this project is not going anywhere.

But something good came out:
A complete day was spent without making a dime, but I got a very good idea from this project which I turned into an app and it's already in the play store now.
As a matter of fact, "Best Call Blocker" my app on Play store was a cross between two different stories. First I described above and second one's related to my 18 months old son who loves to play with my phone. He often makes unwanted calls, to his tiny miney girlfriends as I say :)
While researching how to block incoming calls for the "polygamist client", I came to know how can I block outgoing calls based on dialled number.