That's why I wrote "isolated" (no shared folders, preferably on a separate physical machine, guest additions disabled, etc.).
No, that's just insane. There has been exploits to pretty much all virtualization systems, not just the guest drivers.
Sure, a separate physical machine with no network would do, but what could you possibly gain from running possible malware? Do you expect the software to burst into jackpot mode and magically withdraw all your goxcoins?
You don't run malware. Ever. You decompile it.