http://wordpress.mrreid.org/wp-content/uploads/2014/06/atmos...

the density is low though

observe that where Helium becomes a significant percentage, there is also Hydrogen and (monoatomic) Oxygen.

if one were driven by purism or vanity for stoichiometric exactness, then at a height of 1000 km theres 2 Hydrogens per Oxygen atom, so this could be reacted to water, and the energy used to power compression of the Helium, the water would freeze.

without this vanity, helium becomes a significant fraction at much lower heights... and thus higher densities.

The energy to compress becomes nearly insignificant at low pressures.

if humanity ever builds space elevators, this will be one of many benefits of having space elevators.

The overall amount of helium in the atmosphere is still more than enough for the foreseeable future, and it could be extracted (albeit at high energy cost) by augmenting existing air separation units (ASU's). Of course natural gas wells currently provide an easier to extract source, seeing as the concentration there is way higher.

Space is at the top of the atmosphere right? That place is full of stars producing helium by the teragram.

GP ain't wrong, but the phrasing implied we'd have it closer by than it actually is.

Even if it didn't, collecting it seems wildly expensive.