I was referring to "Professional insurance" and what is often referred to as Errors and Omissions insurance. Professional is the one covering the server you might knock over; E & O is the one covering you when your program should cause an "ouch" to someone's data while working on their stuff. You really might care to consider it if you're working on someone else's systems for long periods of time, especially if you're diong this by yourself.

No matter how good your code is - you can still get sued, especially if you're in there fixing a timebomb of a system. Just being the last one in front of the keyboard when the system goes to hell might be why. For the same reasons you might want to incorporate (as in - keeping the books separate, and keeping your house if something goes "bad" and you get sued), E & O will save your bacon if your bacon is in the pan.

I've had more clients require Professional insurance coverage than anything, followed by Workers' compensation. Disability is your issue so they don't "care" about that.

The other ones are definitively critical as well - I just think of them as non-negotiable, so I kind of take them as granted. As outrageously priced as it seems to be - going without health insurance is, well - stupid with a capital S (when it's within your control of course). If you're employed at all - get covered and stay covered.