Ads on the moon?

So I was twittering about this company that claims to want to put advertising on the moon by imprinting patterns in the lunar dust with a rover of some sort. At first I was just shocked and/or pissed that anyone would think this was a good idea. But then I started thinking about whether such an idea was even possible. After all, for something to be visible to the naked eye on the moon, it's got to be really big. For example, the Mare Crisium is a basin on the moon that's usually visible to the naked eye, and it's 176,000 sq. km.

So just how big would we be talking here? Let’s do a little calculation...