My company does estimates in two ways.

1. Sales person just throws a number out there, always short, and we panic code to make it happen before the client decides twice as long isn't worth it.

OR

2. The devs are told to give an estimate before having a chance to find out all the requirements, THEN ARE TOLD THEY ESTIMATED TOO HIGH AND TO LOWER THE NUMBER!

FUCK THE ESTIMATING!!! GIVE US TIME AND ACCEPT OUR ESTIMATES!! SALES PEOPLE DONT HAVE TO STAY UP IF WE NEED TO CRAM!!

Every one of our sprint "planning" meetings.
We would sit and be told to estimate a bunch of defects we had never seen before. And then we wouldnt actually decide as a team what to commit to because it was assumed that we had to deliver everything in the backlog every sprint. This is what happens when you try to apply scrum to a maintenance team.