No wonder Google can offer free email

"All of the decisions revolved around the central fact that a typical Gmail user was receiving only about five emails per day, most of which were of promotional nature, and as such, required no response. This was in contrast to a typical Googler who received an average of about 450 emails per day, many of which were important to at least read, with a good chunk of them requiring a reply."

Via TechCrunch

Still, is it worth it in return for providing advertising data to Google? [Note: I use a free Gmail account myself so am willing to pay that price - although if there was ever an opportunity to pay to not be used........]