Launching millions of objects into earth orbit doesn't seem like a very good idea to me, especially if you can't recover them in the event you change your mind, but the means of maintaining their orbital stability is not just a pipe dream.

Very small objects, such as dust particles in orbit around the sun, are exposed to solar light pressure which imparts a radial accelleration to them. However, because of their orbital velocity, the accelleration vector resolves into two components, one radial, and one tangential to their orbit and opposite to the direction of revolution.

The effect is related to the aberration of light phenomenon familiar to astronomers, or to any motorist traveling at speed in a hard vertical rain. Due to the car's motion, the raindrops appear to not come from directly above, but from slightly ahead. The net effect is to cause the dust to be both pushed further from the sun, but also to slow down, which causes them to spiral inwards towards the sun. It turns out the latter component takes precedence. This P-R Effect is effective in certain mass/cross-section ranges and solar distances and effectively cleans the near-solar neighborhood of orbiting dust.

Just as a sailboat can beat into the wind, by using solar sails appropriately trimmed it may be possible to tack against light pressure and maintain station in an orbit. The acceleration vectors due to solar wind would be miniscule, but their effect would be cumulative over long time periods. Microprocessors aboard each spacecraft would constantly sense the sun and the orbital elements and adjust the sails appropriately to speed up, slow down, or move sunward or radially.