Is this from Til & Chris ? 

It's on Till Nagel's site...but not sure he authored the UX?  I have seen the Max Plank interactive map, and there are many similarities.  It may even also use the same rotating circle geo type interface.

Just to chime in. I created the visualization above (Showing collaborations in research, see http://tillnagel.com/2011/10/interactive-exploration-of-geospatial-network-visualization/ and http://tillnagel.com/2010/11/muse/ ).
The Max Planck one I did not design. It's a great piece by Moritz Stefaner and Chris Warnow from onformative as mentioned. (They were aware of my similar project, and used the Unfolding library for the two maps, though.)

Regarding the original question:
It's some visual connection style I developed with the aim to have smooth junctions between bubbles and their edges. If you are interested I can publish the code.

Hi Till, publishing that part of the code would be excellent, and i am sure the community would be much appreciative.  I could see that form being an excellent standard way of showing not only how large a datacenter/city/problem is but also how strongly linked one centre is to another through width.  Then color becomes a differentiator.  It's really beautiful.

Apologies for the late reply. I finally managed to throw together some short explanation. Find examples and code here: http://tillnagel.com/2012/11/gum-and-weighted-connections/

Till, i don't think i have ever seen anyone answer any forum question which such beautiful tutorial! Many thanks from all on the forum.