As mentioned "Job Lock" is a very real problem, but it's not as bad as
"Provider Lock" --being permanently locked into a particular insurance
and/or healthcare provider due to a pre-existing condition. In other
words, if you somehow lost your insurance, no one else would insure you.
Being locked into a health provider can be devastating in a number of
different ways.
I'm not sure those are even different issues; if you get seriously ill while on your BigCo Kaiser plan, you're stuck at BigCo; even Kaiser isn't going to cover you if you switch jobs (and thus plans).
You can pretty safely move jobs and group plans even when you have a pre-existing condition, provided there's no significant break in coverage. It's part of the "portability" portion of HIPAA.
Wow. I didn't know that. I yield all my comment's karma to the man whose comment is actually correct.
I think I missed this because portability doesn't guarantee issuance of individual (non-group) health insurance. It's a very good thing for people who change jobs, but not a very good thing for people who want to start companies.
Being locked into a health provider can be devastating in a number of different ways.