If you're in the UK, or have an address in the UK, you can file a statutory demand for payment. That starts a 21 day legal clock, and if they haven't paid after 21 days, you can start putting them into liquidation.
See:
"Make and serve a statutory demand", published by the British government. The UK has tough collection laws.
Bitstamp's registered address is:
BITSTAMP LIMITED
5 NEW STREET SQUARE
LONDON
UNITED KINGDOM
EC4A 3TW
Company No. 08157033
Act now to avoid being caught in another Mt. Gox like situation.
If it turns out that Bitstamp is OK, they'll send you your funds, and you're done. It won't hurt them if they pay.
Why would I want to do that? If I put them into liquidation I turn my claim on my funds into that of a senior creditor.
At that point I am equal to any bank that has lent them money, and junior to any venture capital fund that may have lent them money on a secured basis.
In effect my money ceases to become my money and becomes general corporate funds to be distributed equally between all senior creditors, after any taxes, duties and secured creditors have been paid out. So I am likely to get significantly less than I will get if I wait for them to reopen and then withdraw my money. If they have not reopened in a week or so then think again - but right now what you suggest is detrimental.
That's an excellent point. However, a statutory demand doesn't put them into liquidation; it just gives you that option. That, as a creditor, gives you more bargaining power. Also, it helps prevent dissipation of assets as a dying company thrashes around trying to survive.
Since Bitstamp didn't make their self-imposed 48-hour deadline, and hasn't even issued any new public statements or talked to the press, they're probably in deeper trouble than they've admitted. Worst case, management has run off with the assets and disappeared. Some form of legal or police action is needed. Mt. Gox's creditors waited far too long before acting.