The Internet contains fearmongering about CFL light bulbs as well as insistence that they are harmless and that the concerns are overblown.
Just how dangerous are CFL light bulbs if they shatter and release their mercury vapor? Are we talking one broken CFL light bulb causing brain damage? Or 100 CFL light bulbs needing to be shattered before you’d have ill health effects?
And why do these light bulbs need mercury in the first place?
Here’s an article from National Geographic, probably not a CT site. It says the same things I’ve seen elsewhere, the amount of mercury is tiny and you’d need to break a lot of bulbs to cause any danger, and CFLs actually reduce the amount of mercury released into the environment compared to the amount produced by the extra energy that was needed to power incandescent bulbs.
Here are some previous threads on the same topic:
http://boards.straightdope.com/sdmb/showthread.php?t=419002&highlight=mercury+hazard
And some other resources that summarize what you should do if a CFL breaks:
http://www2.epa.gov/cfl/cleaning-broken-cfl
http://www.nrdc.org/energy/cfl.pdf
Hopefully that should help with your first question. It’s really not worth freaking out over.
I don’t know the answer to your questions, but I can give some personal anecdotes. One day, my father brought home work a pound bottle of mercury (it was astonishingly small) and we used to rub it on dimes and quarters (silver in those long gone days) and they would look bright and shiny from the amalgam that formed. I don’t know what happened to the bottle eventually. Later on, I worked in a lab that had some open containers of mercury, I don’t know what they were for, but it was on an elaborate apparatus. One of we techies was allergic, but most of us ignored it. I still haven’t noticed any brain damage.
On the other hand, hatters used mercury all the time and it did eventually do damage. Mad hatters and all that.
a fluorescent bulb has some mercury in it to allow the flow of electricity through the bulb to produce light.
if the bulb shatters then the broken glass is a greater risk.
the government recommends that you stay out of the room for 5 minutes allowing air to flow, to dissipate if any mercury might get into the air. most of what little mercury is in the bulb will stay with the glass, this should be gently swept up and bagged.
For your third question, the mercury in CFLs is used to provide ultraviolet light - electrons flowing from the ballast within the bulb ionize the mercury vapor in the tube, excited mercury vapor will then release its excess energy as light - some visible, but much of it ultraviolet. That white coating on the inside of most fluorescent bulbs? That’s phosphors, which will absorb much of the UV emissions and re-release that energy as visible light, which is probably why one turned on the CFL in the first place. 
Mercury is used because it’s much more efficient at turning this electron flow into light than other elements.
Sorry, didn’t see the previous threads on this topic. Thanks.
When I was in 8th grade science class, the large lab bench / demo table at the front of the class had an asbestos top. We used to dump mercury onto that and play with it (including rubbing it onto coins). Now I’m a drooling semi-zombie. Who knew?
Yes, it’s a miracle I can type considering that like countless children, we used to roll mercury around in our bare hands, because mercury is so cool!
We lived in blissful ignorance back then. My brother worked for a while in a small factory that made watch and clock faces. During WW2 they made the luminous faces for gauges on Spitfires and other aeroplanes.
The luminosity was simply radioactive paint and had to be applied by hand with a brush and the problem was that the women who dis this fine work, would suck the brushes to get them to a better point. The resultant damage to faces and jaws was pretty horrific.
metallic mercury, while not the safest to mess with, is far less dangerous than organic mercury compounds like dimethylmercury.
metallic mercury vapor is harmful, which takes some heat to produce (boils at 357C). inhalation is an issue if it has vaporized.
so the playing with mercury for a short period at room temperature where all the metal was recaptured hasn’t resulted in our going nuts.
In high school I worked a cleaning job at an office building, and we’d just throw the old fluorescent bulbs out with the regular trash. Oftentimes they shattered when we threw them into the trash bin, which was in the building. No one ever seemed too worried about it.
When ever my CFL bulbs go dead on me, I take them to Ace Hardware, where they supposedly recycle them.