I think most people prefer to remain anonymous. It's much easier. I'd be willing to bet that you avoid interaction for one very good reason. Fear. Fear of spam. I'm sure you've been burned before. You enter a drawing or register for something, and in return you get...spam. I hate that part of the Internet.
Now I suppose there are all kinds of other reasons why people choose not to interact. But what finally makes your potential customers stop lurking and start talking? It takes more than a flashy new guest book. There has to be something in it for them.
The desire for more information is the ultimate enticement for interaction. Internet users are savvy, intelligent people and usually prefer to find what they need themselves rather than ask for help. But sometimes, even after they've read all your faq's and checked every page, their "quest" for info is still not fulfilled. They will look for other alternatives - either another website, or your email.
The trade off becomes... "Ok. I'll share my email with you if you will please just answer my question!" Let your visitors know their email address is safe in your hands. One of the primary goals of your website is to encourage your customers to interact with you. If you can get your website link into their inbox you are well on your way to making the sale.
Often times when I am composing a message, I take on the mind set that I'm probably not going to get a response, at least any time soon. That way I'm not quite as disappointed when I don't hear anything. It seems the larger the company, the less chance there is of getting my information in a timely manner.
Answering your email quickly and accurately is your greatest asset when competing with the major players. Make it your top priority. Become the "Service Leader" in your specialty niche. I like to reply to emails as soon as I get them. It surprises and pleases people, and helps bridge the "fear of interaction" gap.
Email can quickly take up all your time if you're not careful. I have read how many antiques and collectible webmasters are overwhelmed with people contacting them for free appraisals and requests for "more information."
If this is the case for you, state it clearly on your site that you are in the selling business, not free appraisals business. If you find yourself inundated with these constant requests, develop a file of "frequently asked questions" that you can cut and paste quickly to send an almost automated, yet personalized response.
Email is a powerful business tool. Never leave it unanswered. After all, it probably took a bit of courage from someone to send it to you. Respect them for that. Respond quickly!