dstiles - 3:33 pm on May 31, 2012 (gmt 0)
188.8.131.52 - 184.108.40.206 (220.127.116.11/12)
Amazon Technologies Inc.
Amazon AWS Network Operations
Registered late last year, some sub-ranges modified within the past month or so.
Two hits on my server today, widely separated within the 54.247/16 range - sub-listed as ...
54.247/16 - Amazon Web Services, Elastic Compute Cloud, EC2
... a limited spot-check on other /16 ranges does not give that.