I'm not a big fan of URL shortners - bit.ly, t.co, goo.gl, ow.ly, etc - I understand the need for them, but they seem to offer a fairly poor service in terms of privacy and usefulness.
Take this recent example from Vodafone.
Aside from the obvious downsides (user doesn't know where the link will take them, if it's compatible, link looks like gobbledegook, etc) there is a rather more interesting issue.
Goo.gl - along with many other URL shortners - give everyone access to your statistics.
Visiting http://goo.gl/NdVGI+ will let you see everything.
I don't know how many messages were sent out, so it's hard to calculate a response rate.
From the map, I can see the two target areas were UK and (unsurprisingly) Greece. There are a few hits in other countries - that could just be people connecting via WiFi networks routed through that country.
There are also a few hits from iPhones - suggesting either the targeting wasn't accurate, or people are spoofing the iOS user agent.
Still, it's an interesting insight into Vodafone's marketing.