I can see if shared via mates they WILL want to play multiplayer, and if the only way to do it was via a legit copy then good news. Of course, no security system is foolproof...
You'll have to have an account for multiplayer, as your data will be stored on Frontier's servers. There won't be a way to play multiplayer, or even single-player online unless you've bought an account, or are sharing one with a legitimate purchaser. So pirates can only play single player offline, and many will probably then want to convert to the full experience.
Between that and the ability to primarily sell digitally online (with no reselling of used copies, which is something David Braben has criticised retailers for in the past) the stars have aligned for Frontier to maximise returns.