Besides the part where the mirrors fix themselves after an hour or so and it's not worth it to be constantly breaking them?

The people tend to stay on their side of things unless the Queen of Hearts gives them permission to come over here. And since we can't be on the same side as our Mirrors, we get tossed over to their side until they go home to theirs.

::Now Ed scratches at his neck absently.::

They're not all bad--I've met a decent one or two--but most of them, you need to keep an eye on.