What constitutes "misuse"?
The big fears are trying to use one as a weapon is the big fear - slamming a barge at FTL into a colony-station or planet would ruin either - or theft by a foreign power. But since any misjump could be catastrophically deadly, any jump which does not match a planned and expected course is treated as potentially dangerous.
There have been attempts at using them for smuggling, quick business opportunities, petty theft, and - in one infamous incident - a crewmember attempting to evacuate his family.
Notes on tallstone production and implications of cybersecurity
Interesting. There's no way to "ping" the "network" and - by physics or other means - determine how many other cards are on that "network"?
Also, depending on how difficult it is to create Tallstone, this creates the possibility that there would be "certified secure" tallstone from well-regarded manufacturers, and riskier-but-cheaper options if you don't care. It also raises the possibility that beyond individual bad actors, governments or criminal groups could set up entire fabs producing batches with access for them.
Refreshing that the defining system characteristic ... seems to be that it isn't a system.
Exactly. One of the themes I'm aiming for in this world is that magic is something intrinsically of the heart and soul; it's not something which can be objectively studied. You can still try and loosely categorize it and observe similarities, but magic can't be completely separated from the person.
fast travel being inherently scary
Really, I just wanted to cut down on the 'easy fast travel' trope and make the world seem bigger... but it's also a cool idea to play with thematically! I like what you're doing with the social angle as well.
Ah, well. It was a good idea!