Foursquare has launched a new email marketing campaign aimed squarely at increasing the location-based network's user generated content.
Submitted by a Tnooz reader, the email marketing campaign hinges around recent trips by users.
The email outlines several places related to the user's trip, and asks the user to leave tips at the suggested locations:

Your friends and other people on Foursquare will appreciate your words of wisdom!
A "pro tip" at the conclusion of the message also reminds users that they can add tips after the fact by navigating to their history page.
Courting continued engagement is an essential part of any social network - especially one that relies on user tips to increase the overall utility of the tool. It's compelling to see a brand use easily available information - places recently visited - and ask for the user to create more content around those places.
The "always be closing" and "make the ask" crowds will understand this philosophy, and it's important to reiterate it here: you'll most definitely never get something you don't ask for. It might happen organically, but actually asking for a particular action is much more effective than hoping for it.
By engaging loyal users in a post-trip email campaign, Foursquare is not only taking advantage of the post-trip afterglow, but also asking active users to continue to contribute to the community.
For some, this could be construed as an unwanted intrusion, and there's always the danger of losing users to the unsubscribe button. Nonetheless, in the interests of only engaging with the most passionate users, the company can cull the least dedicated from this list - thus both making it a more effective marketing tool for the company and boosting the quality of this particular email marketing list.
As of publication, Foursquare has not responded to Tnooz's request for comment.