Toyota Prius hybrid reaches 3 million units sold worldwide milestone
Some hybrid stats...The millionth Prius was sold in 2008, and it took until 2011 until a million was sold just in the US. In the first decade of its existence, the Prius hybrid sold 1.8 million units, yet only 3 years later we've reached 3 million units sold, a rate at which it'll reach double-digit millions by its second decade. And if you add up all of Toyota's hybrid models, they've sold 5 million worldwide and 2 million in the US.
Part of the Prius' success was because the hybrid got better with each generation, but also because Toyota figured out over time how to make a profit on it while reducing costs (this matters because no product, however green it is, will stick around for long if those who make it lose money):
In 1997, TMC launched the Prius, which was the world’s first mass-produced hybrid passenger car. The second generation followed in 2003, and the third generation in 2009. From the first to third generation, TMC greatly reduced the cost of the hybrid system by two-thirds while improving the EPA-estimated ratings for combined driving by nearly 22 percent (source)
Of course, these days gas-electric hybrids without plug-in capabilities aren't exactly at the cutting edge, but they still do a fine job of reducing fuel consumption and smog-forming emissions compared to non-hybrids. As always, it's better for the environment to walk, bike, or take transit, but if you're going to drive and don't want to get a plug-in, you should probably look at regular hybrids like the Prius (and others, of course).