I'll admit the problem is probably harder for other businesses then for farms, because in many cases even if you can't borrow the money or otherwise come up with it you can sell part of a farm. For a lot of other small businesses it would be an all or nothing prospect.
[link|http://www.washingtonpost.com/wp-dyn/content/article/2005/07/23/AR2005072300741.html|Washington Post]
The numbers that owed estate tax, the CBO found, were paltry, and the number without enough cash on hand to pay the bill even punier: In 2000, for example, just 1,659 farm estates had taxes due, of which 138 didn't report enough liquid assets to cover their tax liability.
And note that isn't 138 that lost their farms, that is 138 nation wide that didn't have enough cash on hand to pay it immediately.
I would agree that $1 million is too low a level for this tax to hit. Like most rates, the government set a fixed rate and doesn't adjust for inflation until enough people complain about it. Given what I have seen I would say $5 million or $10 million would be a better base line.
Jay