Amazon have not yet explained the reasons behind this extraordinary move, other than the usual 'effective business development for the betterment of all' line. One assumes the true reasons will come out directly, or indirectly, and indeed, if there is far more to this move than we are all aware of.
From following the current forum discussions, it seems that POD publishers have the basic issue of a retailer of Amazon's size and weight, dictating to them who they should use to print their books. On a more practical level, Booksurge unit costs are higher than Lightning Source, and the feeling is also that the POD publishers have issues with the quality of print from Booksurge.
On a more personal note, it still seems unclear if the current Amazon situation will affect web listings for Amazon sites outside of the United States. We can only wait and see how this develops.