From what I can see, this possibility is raised by only one organisation, the Association of Americans and Canadians in Israel (AACI). They are trying to make a big campaign out of it, and the story was picked up by a couple of Israeli newspapers, the Jerusalem Post and Haaretz. There were stories in those papers on November 12, then nothing since.
It looks to me like the story is akin to that "Death Panels" story; a virtually baseless canard that is put out there to scare people and convince them that Healthcare Reform will be against the public interest & will cost folk more in taxes.
The AACI have an FAQ about the issue of Excise Tax payable as a penalty by those who don't have health insurance; they are encouraging people to write to their Congressional representatives. The FAQ states
However, both bills do include an excise tax for non-participants. The House bill exempts us from this tax, the Senate bill does not. That is why we are bringing this issue to your attention and asking you to voice your concern to your Senators.
When it says, "The House Bill exempts us.." they mean, "us" as in "US expats." It seems fairly obvious that any eventual legislation will exempt folks who don't live in the US from the obligation to buy health insurance in the US, but I guess anything could happen...
Here is the AACI's page about the (supposed) issue.
http://www.aaci.org.il/articlenav.php?id=163#qanda