A poll asking people whether President Barack Obama "should be killed" has been taken down on the popular social networking site Facebook, and is being investigated by the Secret Service.

According to CNET, the the Secret Service was informed about the poll over the weekend by a blog called the Political Carnival. About 730 people had answered one of the survey's four choices -- yes, no, maybe and "if he cuts my health care" -- before the page was taken down.

The Plum Line, a Washington Post blog, reports that the Secret Service has begun a probe.

As a high-profile African-American presidential candidate, Obama had received Secret Service protection earlier than usual during the presidential race. He has in recent months received intense vitriol from critics, and some pundits attribute the Facebook poll as the latest manifestation of such acrimony.

During Congress' month-long summer recess, lawmakers held healthcare reform town halls that featured angry constituents and Nazi symbols, and that sometimes turned violent and ended in arrests.

Earlier this month, a Republican congressman from South Carolina heckled Obama while the President was addressing a joint session of Congress. Around the same time, the chairman of the Florida Republican Party had accused Obama of "spread[ing] socialist ideology" to children when the President marked the new school year with an address to school children about personal responsibility.

Former President Jimmy Carter has cited racism as the reason for the intense opposition to Obama, an allegation the White House has disputed by saying, "The belief is not that this is based on the color of one's skin but on honest political disagreements that have been going on for -- well, since the beginning of our country."