The most widely known is Azure, when they had to shuffle addresses around:

http://www.internetsociety.org/deploy360/blog/2014/06/ipv4-e...

Google already started charging a nominal fee for idle IPv4 addresses: https://cloud.google.com/sql/, search for "Idle IPv4 address"

It has been an issue for some in the past[1].

[1] http://www.internetsociety.org/deploy360/blog/2014/06/ipv4-e...

Amazon landed the largest address transfer that I'm aware of to date (a /10) when du Pont chopped up 52/8. Reddit mentioned it, but I didn't see news on it:

https://www.reddit.com/r/networking/comments/2tc4ss/looks_li...

They keep buying space. Microsoft for example http://www.networkworld.com/article/2228854/microsoft-subnet...