There really isn't a right or wrong answer for this. Management is more difficult with multiple databases but there are certainly some advantages. With a single database you have to include an additional parameter for every single query to ensure you only get data for that customer. Another option to consider is if this is a web application you will need a new website for every single customer or get really creative with connection strings. Either path has benefits and challenges. The best decision is the one that best fits your situation. 😛