In a short blog postDopplr has this morning confirmed that its rumoured sale to Nokia has completed successfully. The announcement contains this line:

Nokia shares our vision of the Social Atlas, the idea that social location data can improve our experience of cities.
I am interested in this concept of the Social Atlas but best to leave the description to Dopplr themselves:

There are plenty of great sites out there where you can find subjective reviews and star-ratings of places round the world. We wanted to do something different, building lists of the best places ranked by everything that we know about the traveller.
Because of our existing community, we already know all sorts of things about our travellers’ habits – for example, we know who visits New York most often, and we know who lives in Europe. These “opinionated lists” would tell us things like where Europeans eat in Tokyo, or where frequent visitors to New York stay compared to people visiting for the first time.
Taking into account these sort of factors, we can build aggregated views based on the wisdom of particular crowds. It can be interesting to see “people who visit X also go to Y” statements.
Discovering a city starting with places you already know is a great way to improve your local knowledge, but what if you’re new to a city? The Social Atlas has another mechanism to help sort and sift the combined knowledge of Dopplr travellers. We calculate lists of places that aren’t just ordered by plain popularity, but take into account the travel experience and social interconnectedness of people who visit.
So it's about the data. Interconnected data.
One of the challenges with Dopplr is that it relies heavily on the network effect. The network, collectively, becomes more useful the more people join. This is true of most social networks.
Cloud travel itineraries
Putting aside the specifics of Dopplr's Social Atlas what their platform is really about is storing your travel itinerary in the cloud. Once the data is "out there" you can start to find interesting uses for it.
Dopplr are by no means alone when it comes to cloud based itinerary storage. TripIt for example is a strong category leader. The difference with TripIt is that the utility to a single traveller on a single trip is immediately obvious.
No need to keep pumping data into the cloud hoping that the hyped networked effect will kick in at some future point as you do with Dopplr.
Super PNR for direct bookings
Where I think we are going with cloud based itinerary storage is towards a Super PNR (Passenger Name Record) concept.
Imagine the future where travellers research and book directly online via a variety of supplier websites. At that point we need some glue (or perhaps a bucket) to store this itinerary data in one place.
Independent services, with access controls (eg perhaps using OpenID) could access that data and provide either personalised travel advice, latest transport news, suggest other products, give you coupon codes etc etc
Imagine an open eco-system of travel applications just like Facebook or iPhone applications all feeding and updating a central cloud hosted Super PNR.
Does this sound far fetched? Look at what Google have done with centralised records in Google Health. If you can do this with health records it can be achieved with travel records.
Sadly that isn't what Dopplr were building. I don't think that TripIt are building that either! The concept is too big for a startup.... an existing player who believes in direct bookings (rather than distributed bookings) is needed to put their weight (and money) behind it.
If this Cloud Super PNR existed then I expect Dopplr would have been one of the most successful applications using it. But it doesn't, so they aren't.... but as with many entrepreneurial ideas the Dopplr concept has shown us the future.... just we collectively haven't understood it yet.