I like FB in the $4-6 range (10-15x PE). Social media companies can be extinguished in a heart beat and relatively inexpensively (witness MySpace) once the next better plaform is developed.

The tech software start-ups that have developed true name brand staying power and longevity are very short:

Google (killed AOL, Netscape, Mosaic and others), Amazon (competitors are mainly brick & mortar operations), Ebay (owns 25% of Craigslist)