They did this, you know, back in the days of Apollo – they placed a corner-cube array at one of the landing sites. Corner cubes are retroreflectors that efficiently send light back the way it came (like reflectors on strweet signs and jogger’s vests). It worked, too – they got the retroreflection.
It was, I think, very weak. Even laser beams spreasd out rapidly, once you get past their Rayleigh Range, so , Goldfinger’s assertions to the contrary, you don’t “project a spot of light on the Moon!” – you get a really big spot that covers a huge area, and it’s not going to be visible from Earth. So Chairface Chippendale can’t carve a “CHA” into the moon, and we don’t need to worry about advertisers doing that.
On the other hand, there are other ways for advertisers to put messages on the Moon. See Heinlein’s The Man Whio Sold the Moon, Asimov’s Buy Jupiter, or Clarke’s short story in (I think) Tales of Ten Worlds or Tales of the White Harte.