Its the new tablet enabled web... so you can pick things with your finger, hence the size. On my surface I only see two big tiles at first, when scrolling down I see more. AFAIK the top line placement used to be reserved for a few and occasionally handed to the second tier on a rotation. In the new concept that is probably changing. The 3rd and 4th tier blogs will probably never make it to the top of BA, hence the P2B concept?