Also landing something on a space rock might not be a huge win from just leaving it in orbit. You see, even if you manage to attach yorself to the thing (and th

Also landing something on a space rock might not be a huge win from just leaving it in orbit. You see, even if you manage to attach yorself to the thing (and the Philae lander of the Rosetta mission demonstrated is's not easy), the thing usually rotates with one revolution every couple hours. So unlike a cosy stable state vacuum of space with sun in one direction to point the solar panels and Earth in another where you point the antennas, you are now sitting an a pice of material that can freeze you/cook you by convection & Sun an Earth continually change position. Also unlike with a space probe that can have a hot (in the sun) and cold (in the shadow) sides, now you need to handle temperature management from multiple constantly changing angles. Fun! Thats why we don't regularly communicate with NEAR Shoemaker or Rosetta even though both landed on a space rock - they are simply no longer in a working order. That doesn't mean it's impossible - you just need to use a rather more complicated spacecraft for that, than just trying to land a space probe.