Here is a little peek into the future of advertising in your Gmail account. Prepare to see more popping up, colors changing, and new Ad formats being tested the closer we come to the end of the year. Hey, Google is a for-profit company, and the pressure to out-perform the quarterly results year after year is just really big. With a stock price dependent on good news, the temptation to all that virgin real estate in the free-Google products must be simply too large for some of the groups within Google. Gmail will probably carry many more ads in the next couple of months, apart from the smarter targeting on the content of YOUR emails!
Just think about it, now that you are opt-in into Google+ with that same Gmail account, Google can easily start to target ads much better based on your G+ activity, friends networks and stage in life. I'm sure Google will milk this investment really good, as a large number of people, including me, have been using Gmail for a quite some time. So Google could mine all those emails for better targeting, where in the time I've been using the Gmail account went through various life stages. With some smart people in the room, they must be able to figure out what is next in my life, and include that in the personal ad targeting algorithm to serve "better" ads for me. Hey, if it's good for users, why not!
In the mean time, I still receive other people's email in my Gmail inbox, where I never got an answer on the post about the Gmail security breach. This is still an open issue!