I don't think that would tell them much. All-cash requires that the acquiring company either have that cash on hand, go into (further?) debt, or sell new shares to the public to raise the money. Legitimate M&A deals that are in part or even entirely in stock are very common. A refusal to accept anything but an all-cash deal would certainly weed out a fraudster like this one, but it would also eliminate a host of good deals, too.