In case you're interested, June 20th is a Thursday. It's more than that to Facebook, though: apparently that is the day the social network will show off a new product, or as the company puts it, a "big idea" coming from a small team. As to what this particular event -- to be held in Menlo Park -- could bring to the table, you now know exactly as much as we do; with recent talk regarding Facebook's interest in building an RSS reader, that rumor would certainly be a good stab in the dark. What's even more odd, however, is the method by which the press is receiving the invitation: the good old-fashioned postal service. Let us know in the comments if you have any particular theories on what it could all mean.