There's quite a few airports around the world where you'll run into this sort of scam. In Guadalajara, I've had to pay a "fee" to board a flight that I already had a seat on. In Bangalore I had to pay another fee so that my luggage would not go missing or be damaged.
I am guessing corrupt officials basically request money from you for no reason- and it's expected you give it to them (for no reason as well). Then, they just call it a "bribe". But I'm guessing... pardon my cultural ignorance.