Most companies are licensed in offshore countries. This could be a problem since the legal terms could be vague. It is always better to choose license takers from more stable legal ground such as Austria, Australia and Great Britain. Interwetten in Austria, Centrebet in Australia and Expekt in Great Britain are examples of such companies. One weakness in Great Britain is that the tax makes it less tempting to place a bet there.
Old companies have higher credibility.
Bookmakers like Victor Chandler and William Hill have been around for decades. My prediction is that many new betting companies will not last. The competition is hard and lots of money has to be invested. All these questions need to be answered when choosing a bookmaker. The Way the World Wagers.