A whopping 66 percent -- two thirds -- of "young online users" (13 to 21) send more instant messages than e-mail messages, according to a study by America Online. That's up from last year, when just 49 percent claimed to send more IMs than e-mails.

The important part of this is not the number. Individual e-mails are compared with individual instant "messages." IM tends to be more of a conversation, so if you spend 15 minutes chatting with a friend, that might be 75 IMs.

What is interesting, however, is the trend. Moving from one half to two thirds in just a year is extremely fast movement.

Meanwhile, Google's combination of e-mail and IM with Gmail may blur the line between the two media -- especially if the idea catches on and inspires Google's competitors to do the same.