Was Jefferson's embargo a failure?
I would say that the embargo was fairly successful in what it was meant to do. However, at the same time, it was certainly not a great thing because of its effect on the economy.
The whole point of the embargo was to keep the US from getting involved in the conflict going on between Great Britain and Napoleonic France. During the time that embargo was in effect, the US did not go to war with either nation. So, to that extent, it was a success. However, the embargo did not get either Britain or France to agree to stop seizing US ships.
However, the embargo really badly hurt the US economy. So you would not really want to say that it was a good idea since the harm that it did was so great.
So it ends up coming down to how you define failure -- the US didn't get involved in the war so that was good. But the French and British did not change their policies and the US economy was hurt by the embargo.
The Embargo Act of 1807 was largely Jefferson's response to the British impressment of American seamen on the high seas. The act stopped all trade between the U.S. and Europe and also prohibited any trade ships from leaving American ports unless approved by the president. Any approval would then require the ship's owner to post a bond to guarantee its cargo. Jefferson's embargo was a major failure because in his attempt to force the English to recognize the U.S. as an equal partner to the high seas by denying them American goods and remain neutral to Napoleon's wars (Jefferson was pro-French and anti-British)) by steering clear of French warships on the high seas, Jefferson's hard line proved only to destabilize the American economy and anger many Americans.
Jefferson's embargo was liken to cutting off your nose to spite your face...