A recent Prosper S1 SEC filing is a step towards the planned secondary market as this Prosper press release confirms. The secondary market will allow Prosper lenders to trade loans they have invested in. Excerpt from the press release:

…Following effectiveness of the registration statement, Prosper intends to establish and maintain a secondary trading market online auction platform, or Resale Platform, pursuant to which lenders may seek to transfer borrower notes to other Prosper registered lenders. …

Excerpt from the SEC filing:

If Prosper is able to establish the Resale Platform, Prosper intends to charge all selling Lenders a nonrefundable resale listing fee of $0.25 per Note being listed for auction resale, or $0.50 per Note being listed for resale with an automatic sale feature. Listing fees will be charged and collected at the time the listing is posted on the Resale Platform by deducting the resale listing fee from the selling Lender’s funding account. Prosper also intends to charge the selling Lender a resale transaction fee equal to 1.0% of the resale price, subject to a minimum fee of $0.50, which will be deducted from the resale proceeds.

Further discussion here.