"Well-oiled machine" vs. "machine is well oiled".
The first form is something you frequently see with the hyphen (erroneously) omitted; getting the second form wrong is more rare, but still happens.
What I'm seeing a lot more these days, which makes me cringe, is using a hyphen in numbers where it's not appropriate, especially with currency. For example,
A budget of 5-million-dollars was approved...
or, similarly with temporal units:
She was 5-years-old at the time...
Or variations thereon. In all-these cases, there should be no-hyphens!
One of the worst offenders I've seen is the guy who writes the copy for WJLA T.V. news in Wash.D.C..
Hyphens (Score:2)
Regrettably, they don't teach this stuff in schools, it's not well explained anywhere I can find, and most people find it quite hard to just pick it up by example.