Invite Only Advertising
GMail is truly a Google coup. I like having the extra e-mail address and I do think the interface and technology is really cool. I think techies/geeks/Neterati love being in select groups…I love private beta tests. You really get to feel like you're helping make a product better and when a friend uses the tool you might be able to say “I suggested that feature…”
“We have GMail Invites!” Okay, actually we don't, but this phenomenon has been spreading through the web the past couple of weeks, and it has really helped to build a buzz for GMail that traditional advertising could never have achieved. What makes this even more special is that the cost to Google was zero.