You will most likely want to be able to project findings beyond the customers who were actually surveyed. Take election polls as an example. A typical election poll is based on a sample of 2,000 people or so. Just about all of the statistical methods you forgot from Statistics 101 are based on the assumption that the sample is randomly chosen from the population. This means that each person has an equal chance of being entered in the sample, independent of everyone else.
Random samples are the key to collecting projectable data.
Random sampling ensures that you aren't introducing some unknown and unwanted bias into your results. You would be missing the cries of pain from evening or weekend surfers who have to use home dial-ups. There are a few ways to implement random sampling on the web. The first way is true random sampling. To carry this out, you need a list of all the customers in your population.