Little less than 30%, actually. 280k out of 640k total owners of ED have ED in their Steam Library, but many of those weren't purchased on Steam, they were simply linked to the accounts.
http://steamspy.com/app/359320
Looks like the $45 price tag is getting people back on the game too. Average players is creeping back up, which is a phenomenon you see when people start buying the game on sale and getting their friends back in the game who took a Hiatus because they didn't have anybody to play with.
If only it were easier to make new friends in the game.
Thanks for the numbers and the link, I was aware of both and they are about what I had in my head from reading a fair about it over the past months.
I was asking Malpherian for his link as the numbers were the opposite of what you posted and I was unsure if he had a source, or made them up, until he backs up his numbers I will have to treat all of his posts with the same scepticism.
Someone mentioned earlier that a lot of people use steam for the sales to buy many new games, so it makes sense that steam players would play ED less if they have many new games to play.
+1 for the link and opinion on the $45 price tag, I hope you are correct. FD's last accounts ended 31/5/14, IIRC last year they came about this time so we will see how they have done over the last year very soon, bearing in mind the guild stance has been consistently no (in variations of PR approved comments).
And the accounts will be pre xbox and CQC, expansions etc, so more cash still rolling in, I will keep an eye for when they are filed but I know (on the forum) an investor who follows this a lot closer than I and he will likely ninja me by days

. I doubt FD will be posting begging letters on guild websites and offering bulk discounts any time soon.
I think the last report from FD, or the one previous (IIRC links on website somewhere) mentioned a large deal with MS in the pipeline, plus all those other games they made and are still selling and working on.
And there are plenty of people that post on the groups section of the forum if you really want to meet people or barf reddit (but we both know that and I guess you meant an in game mechanic.
TLDR
DBOBE has consistently said no to guilds (as much as he can without throwing money on a fire), I hope he continues to make the game "he wants to play" and "rare and meaningful" gets here soon, KS was a "finger in the wind" as much as cash injection, DBOBE now has serious PC's to run games on with, DK2 etc, I really hope he sticks to his dream.
Now if he brings out "Elite 5 guild wars, the galaxy got Eve'd" in a few years I might even buy it if it looks good, but its not what ED was sold as.