Your employer could fire you, though, if you all of a sudden developed an expensive medical condition. HIPAA would say that's illegal to do, but it'd be incredibly difficult to prove that was the reason you were fired.

That's a slightly maddening thing about many these comments. If you were getting your healthcare through an employer, you had a lot more security both on the pre-existing conditions end and on the keeping coverage end.

I remember several stories in the news before the ACA about employees being pressured to find private insurance or even getting fired because they were raising the group plan's costs. Are you sure it's so cut and dry that it's something you should be maddened about?

Is there any legal basis for that or is that something negotiated by employers with the plan provider?

I don't know the details but my understanding is that it is partly covered by tax law - if the employer kicks employees who get sick off the insurance, they (and all the other employees) lose some or all tax deductions for health care premiums. The employer can, however, still fire people to get around that.