Short answer, pull them out if you can.
The requirement to remove abandoned cables is all over the place in the NEC
372.13 Discontinued Outlets.
When an outlet is abandoned, discontinued, or removed, the sections of circuit conductors supplying the outlet shall be removed from the raceway. No splices or reinsulated conductors, such as would be the case of abandoned outlets on loop wiring, shall be allowed in raceways.
(374.7 & 390.7 have the same language)
640.3 Locations and Other Articles.
Circuits and equipment shall comply with 640.3(A) through (L), as applicable.
(A) Spread of Fire or Products of Combustion. The accessible portion of abandoned audio distribution cables shall not be permitted to remain. See 300.21.
645.5(D)(6) Abandoned cables shall not be permitted to remain unless contained in metal raceways.
725.3(B)Spread of Fire or Products of Combustion. Section 300.21. The accessible portion of abandoned Class 2, Class 3, and PLTC cables shall not be permitted to remain.
725.61(A) ... Abandoned cables shall not be permitted to remain...
... and about a dozen more places.
[This message has been edited by gfretwell (edited 09-08-2004).]