The engagements and eventual breakups of the insurance giants

Less than two years ago, four powerhouses of the insurance industry paired up: Aetna and Humana, and Cigna and Anthem. Alas, the duos were not meant to be. Here is a history of their tumultuous relationships and how they came to a head on Valentine's Day.

Meanwhile... Humana splits with Obamacare on Valentine's Day!

Humana pulls out of the ACA exchanges for 2018, leaving some counties n Tennessee without an insurer. While Humana isn't a huge player on the exchanges (it sells plans in 11 states this year, but had only 204,000 members as of the end of January), the exit sullies the reputation of the exchanges, adding to the belief that they're in a "death spiral"--as Bertolini said publicly on Feb. 15--and adds fuel to the fire of the GOP's case for repealing the ACA.

President Donald Trump tweeted about Humana's retreat: "Obamacare continues to fail."

But some experts say it's possible that uncertainty over the future of the individual market prompted Humana to pull out, though that's unclear. It's also worth noting that Aetna was accused by Judge Bates of pulling out of the exchanges to gain leverage in its Humana merger and not because of financial losses.

Health policy experts say many exchanges and insurers are doing just fine.