The rules are vague, yes. But basically, accidental hexing is just a special case of compel specific to spellcasters (it's a compel against the character's spellcasting high concept), and in general you should treat it the same way you treat other compels. That is, if there is a situation in which you think a compel against an aspect is appropriate, adds something to the story, and causes the character some meaningful difficulty, then offer the compel -- then the player can either accept or buy it off.
So I don't think any of the above is actually what you are asking for, but I think it applies, and I'll tie it in as follows. Imagine you had a character with the aspect Two left feet (because he's clumsy and trips a lot), but he likes to run marathons. Next, add that he's the mayor of the town, so he's on the local media's radar. How often would you offer compels? You're not going to start off every game session by telling him he tripped last weekend and his nose is still sore and toss him a Fate point. That would get boring. But if there's a big important marathon where he's raising awareness for breast cancer research and it's really important and the cameras are on him...
Same thing for your wizard. If he's a wizard, technology hates him. If he's a minor practitioner, it's probably not so bad. But either way, the character shouldn't be hammered constantly, because that would get boring quickly. One thing you could do in the situation (since the character is high profile) is to think about the problem more in terms of reputation. Stuff is failing around him continuously, so folk are going to start calling him "Murphy" (as in Murphy's Laws, not as in the Harry's friend). The news crews are going to be making jokes about what's going to blow up next. He's going to have lawsuits pending. Etc.
Bottom line: I'm not sure what you mean by "is likely expected to deal with technology", but you might want to rethink mixing a wizard with anything technological. If Steve Jobs had been a wizard, nobody would have ever even heard of Apple.