A hypothetical question: What happens if you run a not very great business and an elegant new service starts up with a similar name? It won't "tarnish your reputation" to be associated with a service better than yours, and it might even help your business if customers confuse the two services. Does that weaken your legal arguments?
"Tarnish the reputation of" basically more closely means "changes the reputation of." The purpose of the trademark law is to avoid customer confusion. Say, a brand of detergent always has a blue swish on its box, while another always has a red swish. A customer who is loyal to the former brand, would quickly go through the store and grab the "blue box."
If another company comes in, with a blue box with the same design (a swish, as the above example) and customers mistake that brand for the other, that leads to customer confusion. That Is Bad (hehe).
So if customers are likely to confuse iCloud Communications' brand with Apple's iCloud brand, that's your case there. "Tarnish the reputation" is just a more eloquent way of saying it, thanks to whoever was the clerk that wrote that particular judicial opinion.
Now, if we're talking remedies, then your hypothetical example becomes very important in obvious ways.
(Declaration: IANAL, nor do I play one on TV)