In discussing the midair in Florida, Jason dispenses some excellent advice concerning see-and-avoid but he also mentions that "obviously the controller has made an error ... in IFR there are certain requirements that the controller is bound to adhere to. They are bound to keep the aircraft a certain number of feet apart...". I think this is a common (mis)conception among pilots.
I am NOT a CFI (but I did stay at a Holiday Inn). I have taken the Instrument writtens (actually I just finished all the writtens) and I kept coming across a question that confused me. I thought that IFR meant that the controller would keep me clear of all other aircraft, but that's not the case.
From the AIM - 4-4-11 b.
Separation will be provided between all aircraft operating on IFR flight plans except during that part of the flight (outside Class B airspace or a TRSA) being conducted on a VFR-on-top/VFR conditions clearance. Under these conditions, ATC may issue traffic advisories, but it is the sole responsibility of the pilot to be vigilant so as to see and avoid other aircraft. [emphasis mine]
Here's the deal - IFR keeps you separated from all other IFR
traffic and participating VFR traffic
. If you're in the clouds, you should only have to worry about other IFR traffic. If you're not in the clouds, those VFR guys without flight following do not have to be mentioned by ATC. Seems strange to me, but that's what the AIM says and that's the answer on the Instrument written.