An icon can represent a thousand different words, and that is precisely the problem.
This is just one quote of a thousand I could copy and paste here. A great article by iA about the question(s) why or when to use only icons or only labels or a combination of both. It’s not an article about pro or contra the use of icons or labels only, but it gives you some good advice to think about when you use what.
Thanks for writing this, iA.
The icons you use need to be handled with maximum care. You cannot invest enough time in getting your icons right. Icons need to be recognizable by themselves, they need to illustrate the notion they represent clearly, and they need to work together with all other icons and notions you use, in context.
Oh … before I forget: the crazy bastards even built and released a free game for this. Iconic – the battle between logic and emotion.