[johncolanduoni]

Maybe this is getting blown up by the media, but I've seen a lot of tech people in the UK on HN and elsewhere looking (sometimes desperately) for other opportunities. Even if future agreements don't make it harder for them to remain and work in the UK on paper, it may still cause a lot of skilled labor to leave the UK purely due to perception.

That's assuming that it remains just as easy to do so, which seems unlikely given immigration was part of what was driving the leave vote. Even if it is still easier in absolute terms for someone in the EU to work in the UK than the US, the lowered differential could have pretty negative effects on the market for high-demand jobs.