I'm sure that it's partially because Slashdot is a high-tech oriented site, but it seems like everyone skips to bizarre schemes before considering any of the really simple, really tame geoengineering options available. There doesn't need to be a fleet of aircraft spaying a mysterious chemical to increase Earth's albedo. There doesn't need to be a techniological marvel at the poles freezing CO2 out of the air. As with most things, simple is better.
Look at endeavors like the Marin Carbon Project (links to published peer-review articles within) which diverts waste, composts it, puts it on managed grasslands and improves plant productivity. Some fraction of the plant biomass gets stored below ground for decades or centuries. The dairy farmers don't need to buy/import as much feed which saves them money (and is an additional CO2 offset). Initial numbers look like 1 ton of CO2 per hectare over a 3 year period from one application.
I'm just not certain why we're looking so hard for lots of difficult solutions when there is so much low-hanging fruit. Some pretty simple changes in management practices (I'm looking at you, agriculture) can go a huge way to not only lowering CO2 emissions, but making land be significant net carbon sinks without compromising productivity.
Disclaimer: In the past I worked with one of the lab groups involved with the Marin Carbon Project.