Most regionals do not require a degree, but they often say it is "prefered" . When regionals are hiring lot (2006-2007) lack of a degree will not limit your employment options at most regionals. When times are tough (2008+), most regionals will use the degree as a screening tool to thin their stack of resumes...right now it will hurt you.

At the major level, assume that there is no way in heck that you will ever get a job without a four-year degree. There have been exceptions in the PAST, but few recently.

In fairness, SWA has been known to hire pilots with an associates. I even know one, but he had heavy-duty internal connections. Other than that, an associates is the same as no degree.