By distorting the focus of the photo, the artist simulates the shallow depth of field normally encountered with macro lenses making the scene seem much smaller than it actually is (Wikipedia) and it is particularity suited to cityscapes.
If you can tilt shift a single image then the process is also suited to video clips of the city and the results can be well worth the post processing. The movie below by CeeDee illustrates how using tilt shift urban areas can be made to look like models:
Tilt Shift Test 02 from CeeDee on Vimeo.
The next movie below by Kid Volcano develops the concept with a timelapse tilt shift of a pedestrian bridge in Cape Town:
Tilt Shift Fake from KidVolcano on Vimeo.
The process works with any view captured from an oblique angle - Keith Loutit's example of Sydney is an excellent further example - this time using an actual tilt shift lens rather than faking it in post processing (thanks Bob for the lens info).
Bathtub II from Keith Loutit on Vimeo.
Finally there is a mini San Fransisco produced by Captin Nod:
Dawn and dusk in mini San Francisco from captin nod on Vimeo.
How do you make these videos? Take a look at our orginal post on tilt shift photography for links to a couple of tutorials and then simply create a action in Photoshop to process all of your timelapse frames before creating the movie.
We really like the effect and time willing we will have a London example online soon complete with a walk through of how it was made..