Read an article this past week that said the rumor was that they faked Coulson's death to inspire/bring together The Avengers.
Something I've been saying since the movie came out, and people called me mad!
Think about it, why would Fury fabricate evidence if there was a dead body? It makes no sense.
The fabricated evidence was, imo, only meant to push Cap into action. Caulson was, all things considered, pretty close to Tony, at least the guy in S.H.I.E.L.D. Tony knew the most, so just hearing that he died would be enough to push Tony into action.