A big entity can go to court and the judge might force you to sell the Domain at cost to the big entity (at cost means that if you bought it for $30 you would get $30).
Usually when people try to sell a special name domain to a big entity it depends on how much they ask for.
If are willing to sell for a reasonable price the big entity might pay in order to avoid the hassle of litigation, if you ask too much they will go to court.
I can not tell you what is too much; each case might have its own merit, there are lawyers who specializing in such issues.
:sun:
P.S. I use big entity since this applies not only to corporation names but to famous people's names, commercial products names, and other similar situations.