Speaking as someone who has been headhunted on several occasions by different companies (both successfully and unsuccessfully), I have some disagreements with riot's ruling.

In the past, when an offer has come through without any detailed discussion of my current employment, my general attitude is to say to myself "Is this something that intrigues me?". If yes, then I keep a lid on it and start ironing out the specifics (this does not constitute an acceptance of different employment). If not, then I politely refuse and carry on happily in my life.

The only situation I have informed any of my employers about attempted headhunting was when; I saw an opportunity to show my value to my current employer by showing what their direct competition was willing to offer me (exploitative I know, but I prefer the term opportunistic); or they provided me with knowledge of my employer that they should not have access to.

I fail to see any other reason to inform a current employer of potential job offers.

Where the difference with Riot lies, is the integrity of the competitive sport. Being in the position of trust and accessibility that Deficio found himself in, he has influence over the community. Where his career path can influence others to follow him, especially with his communication of contracted players. If he was offered a job that was apart of the LoL eSports community, I would agree with Riot's demand to be informed. Outside of the LoL eSports community, I see no reason to divulge that information.

TL;DR: Almost no reason to inform your employer of job offers, except when your change in career can influence a change in other factors.