I drop my very old 100 macro (the first ef 100 macro the one all metal without USM). It dropped from about 1 mt but had non problems.
Then i dropped 16-35 2.8, i was taking pictures on a stage, it was near my bag and someone kicket it and let it roll on the floor and droped on the wodden floor a 1.5 m below. Had some damage on the external but kept working... then 135 f2 did not fall but had some kind of bang bicouse i had to fix its AF.
Taking my backpack, but forgetting it was open, i droped 1DII with 200 2.8... camera was fine.. i had to fix AF on the lens.
Then i droped 100 f2 from my backpack in the same way... with the same problem.
Last but not least my samyang 8mm f3.5 fish Eye droped from more then 2 m... and had a circular crack on the front glass, but it kept working witout problems on aps_c. When Used on FF you could see the circular crack on the glass.
The i droped an all plastic and very light 28-80 f3.5-4,5 from about 2m, but it had no damage at all.
Thats all... it is better not to drop lenses.