If you google Quakle you'll find the first page of results are all the media reports on the failure of this platform.
They started off with NO external credit rating of borrowers, obviously a recipe for disaster. My only involvment was to invest the free £30 signup bonus in a loan. It actually made a single repayment, so I ended up with c. £2 profit from the venture.
Who gained ? - the borrowers who quickly realised repayment was optional. What was done about it ? Nothing - ALL p2p LENDERS MUST EXPECT CAPITAL LOSSES.
Squirrl.com folded because they per targeting too niche a borrower sector (service agreements) but nobody lost anything. Yes-Secure / Encash closed because the effort in reworking their business model to comply with the FCA regulation introduced this year was too great for the small volume of transactions they were processing after their earlier lax credit rating led to severe losses for some lenders. I came out with a small profit before tax, but a small loss due to higher rate tax on all interest.
All the other closures have simply been from an inability to gain traction in the market place, with virtually no losses for lenders.
It is upto lenders to consider a whole variety of risk factors before lending on p2p platforms.