Smells like fractional reserves...
Bitstamp was audited by Mike Hearn, a Bitcoin dev back in May 2014. He said that everything seemed OK and all the funds were fully backed in their cold storage wallets. This was just 8 months ago and I'd be surprised if the situation has changed since then.
Yeah, well... This was before the hack, huh...
Now, there are not a million options here:
1. Bitstamp pays $5M with the fees they charged. That's tough, because they had about $1.5M worth of trading each day. At a 0.3% average, that gives $4500 per day. It would take them 1111 days of such fees to pay for those $5M, running costs non accounted for. Impossible.
2. They get $5M from their insurance. I've been working with insurers for such matters myself. Can't find one that would do that, so I'd bet they weren't insured for such a hack.
3. They get $5M from investors. That's tricky. New investors won't be stepping into this mess, so that leaves the previous VC that brought $10M. But this money was probably spent. If not, why bringing it in in the first place? Maybe they'd add $5M to protect the $10M they invested prior to the hack, but that's a dangerous move. Not impossible, but doubtful...
4. They run on fractional reserves. Easy, as long as 88% of the funds remain there.
On which option would you bet?
the owners are millionaires. they are some kind of stars of the slovenian (IT) economy and have won shiny international awards for their company. concerning reputation, much is at stake for them. how much of their wealth would they sacrifice of get out of this mess without becoming karpeles like persona non gratas for the rest of their lives? all of it ? maybe not ... half of their stash? well, i would speculate they'd do that.
if they get this solved they'd be heroes for many people.
It is not 20 or 50 mio, so my bet is that there is good motivation for them to do everything to get it fixed properly. this is pure speculation, i know, but hey...
edit: i have coins there so maybe hope is influencing my judgement