Viaweb's license agreement explicitly forbids spamming, or the sending of mass, unsolicited email. Any Viaweb site that promotes itself by spamming will be shut down immediately.
Viaweb defines spam as mass email sent to recipients who haven't requested email from you, and/or with a fake return address.
If you're not sure if something constitutes spam, check with us first.
Spam is not just unethical. It is also stupid. Professional marketers don't spam, because it doesn't work. Spamming merely labels your company as inexperienced and irresponsible. Who would order from a company like that?