Back in 2000, I bought a large pack of dimmable energy saving "green" light bulbs. They had a 10 year guarantee on them that said if they failed before 10 years, you could mail the entire package in for a replacement (with proof of purchase date etc). That package and the receipt are still sitting in the top of my closet 12 years later, and not a single one of them has blown... I should probably just throw it away at this point since the warranty on them is no longer in date.
There are probably a lot of poorly made ones out there that are indeed to gouge you for your money, but look out for the ones with warranties and guarantees. They're probably going to hold themselves to a much higher standard of quality and lasting power if people will actually hold them to that promise of quality.
With a CFL they just add enough mercury vapor to meet the lifespan they are guaranteeing.
Mercury in the bulb will be destroyed, absorbed eventually, the lifespan is mostly a how much they put in the bulb.