Clan might was originally suggested by the great Bac Ho as the asteroid devastated the sphere and ended the first epoch. Since then the concept evolved to become its current implementation.
The basic idea is that its nice to know where you stand in the pecking order - using your clans strength as the only factor. This is done using the following equation upon each titan in your clan and then adding them together.
Might = Titan Offensive Factor * (number of surviving weapons*2 + number of surviving spawning chambers)
This means that the might reflects your clans ability to fight with existing forces, and breed up new fighters to continue the battle.
Every day the might table is regenerated; its available with the ladders. The might table shows all might scores but does not tie them to clans. Your own turn results will tell you your current clan might. From this you can tell how strong you are relative to your peers.
Analysis of the system within the warcry showed it would be pure folly to let everyone know everyone else's might - too easy to pick a soft target if this was done. So fear, uncertainty and death are preserved. May your wars contain glorious mistakes as your clan takes on an uber clan, and your fighters fall to a wall of the enemy.