http://www.partnersforchildren.org/bulletins/PCHEbulletin3-21-07.html#art9
Article Summary: Unlike incandescent bulbs, compact fluorescent lights contain a small amount of mercury -- about the amount of ink on the tip of a ballpoint pen -- inside sealed glass. The mercury is essential to create the charge that makes the bulb glow. For comparison, the state toxicologist noted that mercury thermometers contain hundreds, even thousands of times more mercury than compact fluorescent light bulbs. Denis Bergeron, energy division director for Efficiency Maine, said that nationally two to three times as much mercury emissions from power plants are avoided by using a compact fluorescent bulb because of the lower energy use. But because of the mercury, these bulbs require proper disposal as hazardous waste. Should a bulb be broken, the mercury can be released -- a problem if at a residence. Maine Department of Environmental Protection officials said homeowners can safely clean up broken bulbs on their own by following careful instructions and wearing gloves, safety glasses, coveralls and respiratory protection. Instructions include refraining from vacuuming to avoid spreading dust containing mercury and contaminating the vacuum. Instead, both the DEP and federal EPA recommend removing larger pieces and placing them in a secure container. Smaller pieces and dust particles can be removed using two stiff pieces of paper, a disposable broom and dustpan, duct tape or a mercury spill kit.
Fluorescent lamps have been with us for a long time. My parents warned to me to never break the lamps as they contain mercury, this is nothing new.
http://toledoohioneighborhoodconcerns.com/blog
that the mercury is only functional (for lighting purposes) as a vapor, mercury gas, if you will. The bead or two of mercury found in most lamps are the inert portion of the equation.
Mercury vapor isn't nearly as easy to clean up as the mercury liquid.