For example, to get to google search engine we just click on it's logo on FD page, but what if we need to get to google maps ? Place two thumbnails for google ? No! We just open the thumbnail context menu and choose google maps ! Yeah ! Same thing for forum sections for example, or tv-programs or evertthing else. VERY nice feature !
There could be some other variants on how to realize this, of course:

• tabs on a thumbnail(crazy, I know)
• mini thumbnails(sounds better)
• additional button in the corner that switches logos on a thumbnail(from "google" to "google maps", from "Logo Requests" to "Styles for FD or UL")
• Rotate button somewhere, click it and a thumb will flip(I'd lovee it !)