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NASA Launches Micro Solar Sail
greyarea67 writes with news that NASA has successfully used a "microsatellite" (a term given to satellites weighing between 10kg and 100kg) to deploy a "nanosatellite" (a term given to satellites weighing between 1kg and 10kg). The deployed object, the first of six in the microsatellite's payload, was the NanoSail-D flight unit. NanoSail-D masses 4kg and is "about the size of a loaf of bread" until it deploys its solar sail.
"...when the NanoSail-D sail is deployed it will use its large sail made of thin polymer material, a material much thinner than a single human hair, to significantly decrease the time to de-orbit the small satellite without the use of propellants as most traditional satellites use. The NanoSail-D flight results will help to mature this technology so it could be used on future large spacecraft missions to aid in de-orbiting space debris created by decommissioned satellites without using valuable mission propellants."
It all depends on the orbit of the satellite, and the purpose of the mission.
A low-Earth orbit satellite will naturally de-orbit due to atmospheric drag, and can be de-orbited in a controlled manner with a very low fuel cost since it just means bringing your perigee down ever so slightly so it burns up. This is good because LEO is the most crowded region you'll find, and the most likely place to encounter an accidental collision.
However, when you start to get up middle altitudes, such as those used by GPS satellites, those things will stay up forever if you don't do anything about them. They're also a lot more expensive to de-orbit, in terms of fuel usage, and even if you do have fuel you plan to use for that, if you lose communications with the satellite you can't do anything about it anyway. Fortunately its much less crowded up there, so a collision is not a very large risk.
Finally, geostationary orbits are interesting, because it gets a lot more crowded again. The costs of truly de-orbiting those is also extremely high, so its not done. Instead, you have what are called graveyard orbits that GEO birds are put into at their end-of-life. This works well enough, but there is an issue of what happens when you have a vehicle die before it can be moved to its graveyard orbit -- this gives you the aptly named zombie satellites that are a significant danger to geostationary spacecraft.
So yes, satellite engineers foresee the problems, but its damned hard to design something that will behave perfectly for years and decades with no capability to go out and make physical repairs. A device to make satellites in high-orbits have the same self-deorbiting properties as LEO satellites would be quite handy.