If the spokes really are loose on the rear wheel, you'll soon start breaking spokes like crazy. Loose spokes break fast due to being loaded/unloaded every time you take a pedal stroke.
The rear wheel on my Giant Cypress broke about 20 spokes the first year. I finally gave up and bought a new set of DT butted spokes and rebuilt the thing, and haven't broken a spoke since (2 years).
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Work: the 8 hours that separates bike rides.