Its not that hard to find who has returned & who hasn't.

He has receivers or members bitcoin address.
Just have to compare it with their GLBSE account, if he sent 90% or 180%.
If its 180%, then i assume he will force them to repay by not returning the assets they have in their GLBSE account.

His only reply after ~20+ days, shows some what aggressive & commanding, instead of requesting or asking or begging.

Since he so far didn't repay any asset issuers their bitcoin, & his commanding reply, shows he has some plans.
Maybe he will just transfer all shares & bonds to LEGAL exchange (Bitcoinglobal).
Coz already, most of the asset issuers identity is known, they cant runaway from government to hide their money, if they do anything illegal in respect to assets they issued.

So for asset issuers, the choice will be transfer all the assets in to new LEGAL exchange & continue business or default assets or get back assets.
Asset issuers cant default, coz it will affect their reputation & future.
Also, getting back assets, will affect their reputation & future business & they loose bitcoins (thats why, he didn't repay them).

So, no good/other way, but go in Nefario's way.