This is interesting: according to some German scholars, the identity of the woman in Leonardo da Vinci's most famous painting has been confirmed by an ancient note scribbled in the margins of a 500-year-old book. They believe this note indicates she is Lisa Gherardini, also known as Lisa del Giocondo, who was the wife of a wealthy Florentine merchant named Francesco del Giocondo. (Curiously, the Mona Lisa is also known as "La Gioconda," Italian for "the happy woman," a little factoid I never knew and which seems to support the Germans' theory.)
I'm somewhat ambivalent about this discovery, myself. On the one hand, items like this always catch my eye, because I enjoy history and the pleasant "a-ha" feeling that comes from making a hither-to unknown connection. I also find it fascinating that there can still be a book with the handwritten notes of a centuries-dead man in it kicking around after five centuries, and that someone can be idly paging through it and suddenly notice something that no one has ever caught before and suddenly we have an answer to an age-old question. And yet there is also pleasure in mysteries, especially the ancient and essentially unsolvable ones, and part of the appeal of this particular painting is the questions that surround it: who is this woman, and what (if anything) is she smiling about? Wouldn't finding that woman's diary and answering those questions once and for all defuse some of that magical quality that surrounds the painting?
To use another example, it's a lot more fun to think about the possibility that there might be a Loch Ness Monster than to definitively know one way or the other. If you find the rotting corpse of the thing washed up on the shore, then you know that it was never anything more than a giant mutant otter or something, and it becomes mundane. And if you somehow prove that there's absolutely nothing in that lake, well, then you lose all the fun of thinking that maybe there was something there.
Ultimately, of course, it doesn't really matter who the woman we call "Mona Lisa" actually is. The painting remains what it has always been, a beautiful work of art and a touchstone of Western culture. As SamuraiFrog asks, does knowing the identity of the woman in the painting enhance your appreciation of the work? It doesn't for me, and in fact it arguably diminishes the experience of viewing it... but damn if I didn't rush to click through to that news item anyway.