I've had previous co-workers and managers contacted as part of a background check. I imagine the companies I worked for were contacted as well, though I don't know that for sure. As for actual job references, it's been less about the company itself and more about the people I worked with.

For example, I worked at one company for a number of years. Eventually, I left that company and worked at a different, unrelated, place for several years. Then, when I was again looking to change jobs, one of my previous co-workers at the first company passed my resume to his boss, who had also worked with me at the first company. They were looking to hire someone to be a contractor for a third organization, and the person responsible for managing people at that third organization was also someone I had worked with at the first company. They all remembered me and had liked my work. Basically, my resume bounced from desk to desk with everyone saying, "yup hire this guy."

You never know when the people you have worked with before will be the people who get to decide on hiring you later. Always try to leave on good terms, it may come back to you later.