Do you know what another name for spam email is? Unsolicited commercial emails.
What your software does is gather emails of people who did not give you their explicit permission (by opting in) to send them commercial emails.
Let's say I start a list in IM. I offer a report called "The #1 secret to generating traffic through Twitter" for free on a squeeze page. Someone decides they want and they opt-in. No trickery here.
By opting in for this Twitter traffic report, they show me that they are interested in Twitter and in generating traffic. Therefore, if I promote stuff related to Twitter, traffic gen, or even social media in general, I can probably get a better response rate than if I were to promote random IM stuff.
From what I can tell, you're emailing a bunch of people who have never heard of you before. They have not shown an interest in you. They have not shown an interest in learning or buying from you. And, again, they have not given you their permission to market to them.
You mentioned sending sales emails to a generic list of people. How can the list be generic if they opt-in to receive a specific product (such as a Twitter traffic gen report)? How could they have been tricked into giving their email to me if they knew what they were getting in advance, and, upon going through the report, liked what they say?
Do you know what's worse than being tricked onto a list? Being forced onto one.
Even if what you're doing isn't illegal, it's still unethical.