sammy007 as far as i know every squeezed margin position on Polo got paid back to the lender, i have yet to hear about someone who did not get his coins back. 2.5x leverage aint that big of a leverage to risk that... i think polo´s liquidation algorithm is good enough for that. Also like i said before... if you are afraid of losing it, put it into cold wallet.
One or the other will inevitably occur: liquidation loss (small) and/or exchange hack/bankruptcy. Polo is AFAICT a very tight ship, but it is not immune to physics. We cannot diversify and decentralize fast enough for me. We are outgrowing Polo. Competitors will recognize this soon enough.
I haven't heard about anyone not being paid back a loan on Poloniex. This indicates they have tight algorithms for illiquid markets. What would tell you otherwise?
As for lending the only thing I wouldn't lend is BTC since it is what gets stolen. Who would spend months figuring out a way to steal XMR when the only real market is the same exchange they would hack? And when you consider the recent hacks of Bitstamp, Shapeshift and BFX you'll find in comparison to the older ones they didn't lose all their Bitcoins and just like the others BFX is still up and trying to make their customers whole. Shapeshifts architecture didn't affect users and Bitstamp covered them.
You'll notice I left out Cryptsy and maybe some other smaller exchanges I haven't heard of but to me this was a long time coming.