They're trying to temporarily blind the helicopter pilot and crew, to make it difficult for them to observe or attack the protesters, on the assumption that it may be part of the regime's forces.
There was a picture up yesterday of a helicopter being painted by at more than a dozen laser pointers.
Even ordinary green laser pointers tend to shut down night vision - both obscuring it with after-images and constricting the iris. There are also some powerful ones - capable of damaging the retina before the blink reflex operates - on the market. The protesters getting their hands on some and using them in this way is a brilliant tactic - no pun intended.
Note that shooting a laser pointer at an aircraft is a major offense in the US and the law is strongly enforced. Point a laser pointer at a plane or helicopter here and you're likely to become the target of an immediate aerial manhunt and prosecution. Blinding pilots currently in control of an aircraft - especially helicopters, which will crash if not intelligently controlled every minute - is no joke.
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"Obama’s Economists: ‘Stimulus’ Has Cost $278,000 per Job."
That means: For each job "created or saved" about five were destroyed.