Dr. Laura, you asked, "What do you think are the top reasons why people get fired?"
I believe it's a sense of entitlement.
An employee is there to provide value to the employer, and to receive pay and benefits in exchange. It's a mutually beneficial relationship, begun with both parties' consent, and severable when it stops being beneficial to either. The employer isn't a charity. The employee isn't a slave.
These days, many employees regard the employer-employee relationship as adversarial, however. It's manifest in bad attitudes. It shows up in habits designed to accomplish the bare minimum work, while otherwise treating the workplace like an Internet cafe. It often appears in the active undermining of peer morale. Employees validate each others' nonchalant attitudes, and these discussions poison new hires' perceptions of the workplace.
I don't know if it's the Occupy Wall Street mentality. Maybe big government social programs have reduce the perceived value of employment. Maybe a good work ethic requires a father figure, who is increasingly absent. Maybe it's the ridiculous portrayals of the office on TV. Maybe fewer employers have backbones, and act like parents who try to be their kids' best friend instead of a guiding hand.
Maybe it's several or all of these.
But it seems like a big reason people get fired is: They forget that they are there... the only reason that they are given an opportunity and a paycheck... is to provide good value to the employer.
If they aspire to anything less, then they lied when they filed an application and accepted that job.