On a whim, I typed mac.com in my browser, and it redirected to Apple’s official Mac page, at apple.com/mac. This worked for more specific domains as well, like macbookpro.com, macbookair.com, and imac.com. But not macbook.com, iphone.com or ipad.com.
On the Google side, android.com works, but not nexus.com. chrome.com, chromebook.com and chromecast.com work, but not chromebox.com, chromebase.com or chromebit.com. That tells you which Chrome ones have been successful.
Apple should buy iphone.com. They can easily afford it, and it generates a revenue of $20 billion a quarter, so the relatively paltry sum it costs to buy the domain will probably pay for itself.
If your product brings in a billion dollars of annual revenue, it had better have its own domain name.