it's a bit like earth, there are places that are inhospitable, but still can have human presence,
then of course there are places that are extremely inhospitable, places that only with up to date technology can people maintain there presence, and even then only for a short while (technology can only circumvent so much, there are other variables that must be taken into account that have nothing to do with technology)
to answer your question, the 50% rule is there to let you no the hospitably factor of the planet/moon in question,
the lower it is the more it will cost you to maintain your presence, but as you have the resources of an entire empire at your disposal, it will take many bad worlds before it effects your overall balance sheet if you will,
just remember though the cost must weighed up by you,
and the effect is cumulative, the steady increase of resources needed for each worlds that looses starts to add up,
although in real life research would play a significant large role in what planets can be colonized, and how bad a colony could be settled, the worse the world is, the far greater technology would be needed to compensate,
(terraforming concepts is not apart of this game unfortunately, as this would be a real life element, and something Space Empires did quite well)
DW will more and likely introduce terraforming system in a later expansion, as like you have rightly pointed out, the 50% thing is not overall fitting, and does and is a after thought system put in place, effective it maybe, but very simple in design and nature.
terraforming is a more realistic approach, and should take a long time to complete (research levels, planet quality level, planet type and size variable would need to be taken into account)
the current system just doesn't take into account species natural climate, and the fact that people (beings) have a voice,
there are some planets that a certain species would never live on, there are some planets that if beings were living on, would leave at the earliest possibility.
terraforming is needed in this game, but so are so many other things, DW is IMO so far from coming even close to being finished.....
but here's looking forward to the expansion (as things like this are way outside the scope of a patch, in fact it was a patch that came up with the 50% thingy)
< Message edited by Registered55 -- 9/1/2010 2:15:51 PM >