I just went though this for my business. I am based in the USA, and I am a small LabVIEW consultant.
There are 3 types of insurance you generally need for a business. General Liability, Workman's Compensation and Professional Liability (aka Errors and Omissions).
General Liability protects you if someone on your premises falls and wants to sue you. Mine has an additional rider called Baily's insurance. This covers equipment not owned by you. If you drop it, and break it, your Baily's will cover it. This is not expensive insurance and is great value for the money. There is also some product and data loss protection in my general liability policy.
Workmans Compensation is if you get you hand chopped off at your customers site or someone working for you. It will pay for your (and employee) medical costs, and protect you from some liability. This is generally what customers want to see you have. Having this insurance protects the customer from getting sued by you if there is an accident (that is why they want to see it). This insurance is based on your payroll. It is not that expensive because computer programmers are at a low risk to get injured. (I got into the accountants category). In the US Workman's Compensation is by state. Michigan workman's comp laws are different than Ohio. If you have employees you MUST have workman's comp
Professional Liability (aka Errors and omissions) protects you if you mess up and somebody wants to sue you. The thing you really want is the insurance company to pay for the lawyer. Legal fees will KILL you. I am more concerned about the cost of litigation than the amount somebody would potentially sue me for. Professional Liability insurance is expensive, and most folks in the insurance industry don't understand what we do. I went through IEEE. They spent the time to find an insurance company and explain the risks of our job. That means better and cheaper coverage for us. IMHO it is very rare to get sued. The costs of litigation for both sides usually causes cooler heads to prevail. However it only takes 1 a**hole...
Reason does not exist in a legal situation. The judges, jurys, and lawyers have no clue on technical matters, and don't care. You could be totally in the right and be liable. Having a big bad insurance company with an army of lawyers on staff who don't want to pay claims is what you are paying for.
Using a building contractor analogy, having LabVIEW certification and insurance you are now "licensed and insured". IMHO this is a very marketable thing.