The Moon is slowly moving away due to tidal interaction. If the Earth and Moon were tidally locked (both presenting the same face to each other at all times) then the orbit would remain stable. If the Earth would be spinning slower than the Moon, then the Moon would be slowly pushed inward.
An interesting consequence is that in a billion year's time, after Earth's oceans would have evaporated, this tidal interaction would greatly reduce, "fixing" the Earth-Moon system in place.
An interesting consequence is that in a billion year's time, after Earth's oceans would have evaporated, this tidal interaction would greatly reduce, "fixing" the Earth-Moon system in place.
More here: http://www.talkorigins.org/faqs/moonrec.html