Oil broke above $100 a barrel yesterday for the first time since October 2008. The culprit: Uprisings in Libya sent as much as half of the country's petroleum production offline.

You remember what happened last time oil prices were this high: Consumers stomped their feet and said no thank you. Annualized, we drove 11 billion fewer miles in March 2008 than March 2007. Air travel fell 2.3% that year -- more for strained carriers like United (Nasdaq: UAUA) and AMR (NYSE: AMR). Trips to the mall, down. Trips to Grandma's, down. Vacations, down.

When it becomes expensive to move, people stop moving. Alas, so does the economy. While expensive oil obviously wasn't the only factor, many respected analysts blame $140 oil as the tipping point that sent the economy over the edge in 2008.

You can say, or hope, that today's price spike is temporary -- driven by geopolitics, not rising demand, as it was then. But 2008's spike was temporary too -- only a few months, really. The only temporary benefactors, oil giants like BP (NYSE: BP) and ConocoPhillips (NYSE: COP), saw their shares plunge 50% or more as the tide went out. It only takes a few months of pain to do serious damage.  

And here we are again.

In 2009, economist Nouriel Roubini said "If oil goes to $100 today, it will have the same effect on the global economy as what $147 oil had last year."

Who knows whether he's right? Today's economy is stronger than it was when he made those comments. But his warning shouldn't be ignored. The psychological impact alone of $100 could send consumers retreating.

Take the Fool poll below and let us know how $100 oil will affect your behavior. Drop a thought or two in the comment section below while you're at it.

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