Hitbtc is one of the worst "top tier" exchanges in the space. They have been selectively allowing people withdraw, and those who they denied withdrawals have been asked to submit id and whatnot to constantly reject them for either being low res, not appropriate format, etc. This reeks of a fractonal reserve model where they do not have the funds available for people to withdraw.
The question then is....... What are they doing with the funds? Invest? Trade? Run an off-exchange lending business? On top of that, they also inflate their volumes artificially. Wonderful exchange.