A short time ago, I linked to a Mark Evanier piece about hitting deadlines. I believe strongly in behaving in a professional manner when working on a project. I also believe strongly that professional conduct goes both ways and that studios have the same obligation to behave as their employees do. In that piece, I mentioned that "the people setting up the schedules or passing judgment on work are often ignorant. They create impossible schedules or ask for changes that will take enormous amounts of time." There are also cases where studios are dishonest with their employees because they have run out of money.
The latest example of this is a studio with the unfortunate name Fake Studios in Montreal. They have yet to pay visual effects artists for their work on Piranha 3D. Variety has the details. The story was also reported and commented on at The Animation Guild's blog. Visual effects artist Scott Squires has posted an excellent list of actions employees should follow to avoid being taken advantage of.
The bottom line is that if a company misses a payday, stop working. The company will use guilt, telling employees that they are disloyal if they don't work, that the company is a big family going through a tough time and that everyone has to pull together. The company may threaten employees with blacklisting if they don't cooperate. However, an employee without a paycheque is an ex-employee no matter how much a company wants to convince people otherwise. It's important for artists to understand this.