Perhaps you could also as "Why is it bad to ask poorly formed questions?"<p>If you're engaged in billable time practices, responding to e-mails is little different than phone calls, faxes or letters. It's all about the time you spend engaged on the work for the client.
I wouldn't say that it's "bad", but, personally, I don't think it'd be in my best interest to use a pay-wall.<p>Most of the emails I get are from people who want my money (vendors/businesses). But I get the occasional email from someone who wants to give me their money (a potential client). I wouldn't want to do anything that would stop a potential client from sending me an email.<p>Two other concerns:<p>1. The practicality aspect. If I'm requiring bitcoin, then the sender needs to be bitcoin-literate, which not everybody is. If I'm requiring a credit card, then the charge is too small to justify the merchant charges.<p>2. The branding aspect. Do I really want to be known as someone who charges for emails? I'm not sure that message would align with very many people's personal brand/image. I'd be more likely to wait on the sidelines until charging-for-emails is commonplace, then I'd feel comfortable joining in. But until that time comes, you might have a first-mover-disadvantage. This creates a problematic catch-22 for any SaaS/PaaS offering this kind of thing. (Few people wanting to be an early-adopter).
This could use some elaboration.<p>Charge who? Your clients? Businesses trying to contact you? Everyone?<p>How? Do they have to pay before they can even send it? You send them a bill afterwards?