I too am unhappy with people who have oversized bags. It is irritating if you cant fit your bag in because of all the others. BUT to me the real problem is when the oalf with the oversize bag tries to make it fit and your luggage is in the same bin! Sometimes they will squeeze your bag or push or shove it against your bag. They have no compunction about trying to stuff it in. I have seen these idiots break things belonging to other passengers. On one flight, the mope finally got his bag in and as we took off the bin started leaking fluid onto one of the passengers. Upon examination, it was found that he had broken a bottle of insulin belonging to another passenger when he stuffed his bag in the bin. As a consequence of all this, I watch very closely what happens to my bag every time until I see all the luggage is stowed. I have even yelled at passengers to cease and desist- and called the FA to take appropriate action. God forbid you have glass or something breakable in your bag.