>I don't think it's reasonable that a simple silhouette of a phone, used as an icon to represent a phone, is trademarkable.

Trademarks are an interesting case, though. You can trademark common ideas, especially if you're the first one to get the trademark for that specific use. They're extremely focused in that they can only be used in a specific way. MS' trademarks on Windows and Word, for example, only apply to operating systems and word processors.