Is centralization in the Lightning network inevitable? Why (not)? Especially keeping in mind the possibility of single-funded channels (see Tadge's Google Doc Slides), buying from an exchange and concurrently opening a payment channel on the Lightning network would seem a particularly simple entry to the LN. 

Exchanges and payment-providers would therefore seem to be in a natural position to become well-connected. 


Is it fair to expect emergence of a network topology strongly centered around well-connected nodes such as the aforementioned and other liquidity providers? 
What incentives are there for establishing additional connections with less well-connected nodes? 
Is it reasonable to expect the network to "flesh out" with alternative connections around the center nodes?
“Centralization” is now a word constantly repeated but is one that, generally speaking, 
   no one tries to define accurately.  ---Alexis de Tocqueville, Democracy in America, Vol.1, Part 1, ch.5. 


Lightning Network channels will naturally tend to form along the paths of economic
activity.  If you assume (as I do) that most economic activity in
Bitcoin today is from individuals to large Bitcoin businesses (mostly
exchanges), then you should further assume that most channels will be
between users and those very same large businesses.

You can call the centralization if you wish---but it is not a
centralization of Lightning's making; it is a centralization that already
exists for Bitcoin users.

Moreover, even though Bitcoin commerce and trading is dominated by large
businesses, there are quite a few of those large business.  I haven't
looked up figures, but I would suspect that Bitcoin commerce has a much
less centralized distribution than mining at the present time---and with
new businesses offering Bitcoin-payable services all the time, Bitcoin
commerce would seem to be in a steady of progressively becoming more
decentralized.