Even though liquidity was what really killed MF Global, the reason that the company was susceptible to a liquidity run was because optically the amount of capital at the institution looked extremely low. Today there's a lot of chatter surrounding Jefferies, but from a pure leverage standpoint the two are hardly comparable.
MF Global Assets: $41B
Jefferies Assets: $45B
For roughly the same amount of assets, Jefferies has more than double the capital.