I may have missed this in some other post as I have not read through them all, but has no one yet mentioned Apple vs. Apple. Apple computers DID get hit by Apple Records for that name. It was decided that so long as they weren't in the business of making music, so long as they were Apple Computers, all was well.
When they brought out the iPod, Apple Records hit 'em again, and there was a tussle over whether they were infringing on Apple Record's territory. Again, it was settled.
I think that kinda shows the biggest problem of all with iCloud here. Which is that the two are very different things--unlike, by the way, App stores labeled App stores selling Apps. Apple Records had a case, but the resolution came when it was clear that Apple Records could not be confused with Apple Computers. iCloud may have a case, but I don't think it will be resolved in their favor if they can't also prove that what they are selling is identical to what Apple is selling with the name iCloud.
I also find it interesting the way people are taking sides here. Some view iCloud as the "little guy vs. big-mean-Apple!" and others as a small con man trying to bilk deep-pockets Apple out of money. I don't know enough about iCloud to cast aspersions on it or its choice of name--and until we do, I don't think it should be cast as a grifter. Likewise, just because Apple is a big corporation doesn't mean that it should automatically be cast as a villainous Goliath.
I would presume that Apple looked for the iCloud trademark, found it, paid for it, and went ahead. If iCloud didn't put itself on the map by registering that trademark then Apple can't be seen as deliberately trying to crush it. At best, it accidentally stepped on it and iCloud is now protesting that. If iCloud has a case, and I'm sure Apple's very well paid and expert lawyers will find out if it does, then they will settle the issue somehow. If iCloud is bogus, no case and just trying to rip Apple off, then Apple again, has every right to go ahead with a court case.