[adrianhoward]

Think of it another way. As a startup getting feedback is your primary tool for improvement.

It shouldn't be a case of offline or online. Do both until you can't. Then start optimising.

I often see organisations cut-off e-mail feedback long before the noise from spammers, auto-replies, vacation mail, etc. becomes an actual issue.

Wait until you have a problem. Then look at the many tools around that can help alleviate those problems. Then think about maybe recruiting more people to help deal with the feedback. Then - if you still have a problem - start thinking about removing communication channels.

It should be the last option - not the first.