Sorry for posting this in the wrong spot...
You didn't post in the wrong spot, this section is public and so is indexed by search engines, and it is this type information on Prosper that needs to get out to prospective lenders, since Prosper seems bent on a cover up campaign as to real returns. Your post was moved for this reason, not because you did anything wrong.
...You are entrusting every loan in your "portfolio" to a single company, and not GE or Coca-Cola, but an internet startup with private financial statements, an untested business model, recent competitors, and incompetent management.
Just to add to this, remember that money put into Prosper is MORE than just gone... it really has no value, or at least a value that is seriously diminished. If one invests in a CD, stocks, bonds, one can remove the money at any time (albeit with possible penalties), but at least some of it can be recovered... these investments have value in the real world, even if greatly discounted.
A Prosper promissory note, on the other hand, is basically an IOU which has no backing except from an individual, and hence worthless to others; there is no market and we are prohibited from selling them anyway. Trading US dollars for worthless paper is really not a good idea, and looked at in those terms, one might be better off trading junk bonds or penny stocks.
The edit ---> Funny thing is, looked at in this way, junk bonds or penny stocks have the possibility of returning tremendous amounts of money, perhaps double, triple, or much much more... yet with Prosper, the possible return is capped by the interest rate, so profit is in fact limited compared to other risky investments.