Yes - employees can earn points in all the same fashion as a non-employee with one exception: associates who use the employee discount for a hotel stay (where they are required to pay a trivial fee and taxes) do not earn points in this scenario.
From the MR Conditions of Enrollment: "Employees of the Company are ineligible to participate in the Rewards Program." It's always been my understanding that Marriott employees weren't allowed to be members of Marriott Rewards, but what Pingreeman said makes sense...of course what makes sense isn't always what is.
NU - To clarify, associates can have a MR account and can earn points via their VISA card and other partner programs. They "could" earn points and nights with a paid stay, but that would be ridiculous given their "taxes-only + small fee" discount. The real restrictions are that no elite status may be earned and no bonus program participation while an associate.