Use the same common sense when looking at what your customers are doing on the Web. It is business, not personal. Be very clear on where to draw the line. E-businesses have privacy concerns, just as consumers do. Especially with B2B sites, companies are often opening up their entire enterprise to the public, a potentially vulnerable situation.
Security is a big part of the picture, as is full disclosure and responsibility.
Show your customers that you are serious about protecting their information, just as you are serious about protecting your own. Let them know what you are doing with it, why, and what's in it for them, and they'll be more inclined to share. Plus, give them just as much access to the information they need to do business with you.