It's not something new. There are lots of projects around the world trying to solve it. As with all issues of preserving knowledge, you'll find that even the simplest things can turn to great pains. For instance - you have your great hole in the mountain for storage of nuclear waste. Now, you don't want people in the future walking down there. Assuming they dont speak your language, what do you do? Paint something, like pic 1: human outside, pic 2: human going in, pic 3: human dead. Sounds good eh? Try reading it backwards, as some cultures do. Human dead, goes inside, comes out alive? Not really the same thing, but it's an interesting problem. What will we leave behind? Not many things are written in rock any more.

All this makes me think of Stanislav Lem's "Memoires found in a bathtub", which is a grat book for those of you who haven't read it.