I though that Celina's question "How do retailers/merchants promote their deal and does it cost money?" in addition to someone elses question "How do they track their success?" were both really good, important, and something I had overlooked in my presentation. And since I couldn't answer the questions really well at that point, I wanted to make sure I do answer them so that if you want to implement a geolocation strategy in your workplace you know how it works in the backstage.
I will use foursquare as my model, knowing that the other applications have a very similar retailer system.

1. There is a back-end infrastructure for businesses and guides on what will work best for your business (see foursquare venues page and click on "Foursquare specials").

2. It is FREE to claim your venue and set up your special promotion (for now, although their "terms of service" says they may charge for this service in the future- which may be a good hint at their plans for money making as time goes on).

3. You can design your own badge for your own event or venue, but they will charge for that.

4. I also recently came across a retailer that created a pop-up that appears when you visit their website, that reminds you to check-in on Facebook places when you visit their actual store for special deals- which is great because it encourages people who may not have otherwise thought to do that to check-in, which makes it appear on their Facebook which is then a free promotion.

5. The back-end infrastructure also has a "stats" portal that can help retailers track things like:

• Total daily check-ins over time
• Your most recent visitors
• Your most frequent visitors
• Gender breakdown of your customers
• What time of day people check in
• Portion of your venue’s foursquare check-ins that are broadcast to Twitter and Facebook