Hum... Xcerion, the previous owners of icloud.com, were based in Sweden. iCloud Communications is in Arizona.
What claims would an Arizona company have over a Swedish company exactly ? They're not even in the same country. However, Apple is a US based company and falls under the same jurisdiction as iCloud Communications.
It has nothing to do with deep pockets or trying to work with the previous owners of iCloud.
Come on guys, this isn't the first time Apple doesn't check before using an iSomething.
iPhone ring any bell ?
http://newsroom.cisco.com/dlls/2007/corp_011007.html
Registering a trademark is not obligatory. Failure to do so does not make the trademark invalid at all. It is completely optional.