Didn't Drexler propose something like this?
Gina "Nanogirl" Miller
>have a big sail,
>> built from nano- or micro-machines. Let debris rip through it,
>> some easily repairable holes and leaving some of the machines on
>> debris. When they are removed from the sail, they start digesting
>> debris and converting it into a small, inert sail. Using some
>> navigation (make an angle of X degrees with light of this spectrum)
>> they either drift away from orbit, or merge with the sail which can
>> digest them.
>Anders this is the coolest thing I have seen in a long time. Did you
>think of it? spike