Recently, I was having a conversation with a friend about daily deals sites, specifically Groupon, when it sort of dawned on us that the line separating spam from not-spam is razor thin. For her, the regular emails had become an irritation and she no longer had any interest in hearing about cheap haircuts or pizza or skydiving; in essence, she now considers Groupon emails spam. I’m the opposite. Even though I’ve only purchased one Groupon in my life, I still find value in the emails.

So how about the rest of you? Do you even open those emails anymore?

Apparently, most of you do at least a few times a week, if not several times a day, according to February 2011 survey data from eMarketer. The marketing and media intelligence group found that 22 percent of subscribers access daily deal emails several times a day, 38 percent access them once per day, and 23 percent access them a few times a week. That’s a grand total of 83 percent of respondents who appear to still find value in those daily deal emails.

That leaves just 17 percent of people who only check the emails at most once a week.

Of course, eMarketer’s use of the word “access” is a little ambiguous. (Are users just clicking “Newer” in Gmail to quickly scroll past all their unread messages?) Either way, I think the numbers are significant.

Even more surprising: over a third of those same Internet users forward daily deal emails to family and friends at least a few times a week. According to the data, 12 percent forward an email several times a day, 10 percent forward once per day, and 17 percent forward a few times a week. That’s some incredible visibility for daily deals and shopping sites.

Overall, eMarketer says users subscribe to an average of nearly three daily or weekly shopping emails or newsletters, and 56 percent of users subscribe to at least two. That means more than half of the U.S. Internet population is receiving shopping deals in their inbox. And of those, “nearly half were still excited enough about them that they said they ‘can’t wait’ to see the latest deals in the messages.

It is with little wonder, then, that daily deals is estimated to be a $4 to $6 billion market by 2015.