The marathon was very careful with how they worded their findings, but overall it says that he did cheat. Notice that they didn't say "after viewing all the evidence we have concluded that Mike Rossi did run the race". It says that after viewing the evidence that can't prove that he didn't run the race.
There is a huge difference.
I don't have any pictures to prove that I banged Kate Upton, but you don't have any pictures to prove that I didn't. So as far as I'm concerned that makes it true.
But then by saying they are adding timing mats and video cameras they are essentially saying, "We didn't catch him this time, but there won't be a second time for him".
So he got away with it this time. But he has a Boston medal and a story about a principal's letter that he can't tell to other runners without the chance that he will be laughed at. Look at it this way - can Barry Bonds brag about his home run record when everyone knows he juiced?
The only thing running Boston is good for is bragging rights and we have taken that way from this cheater. His name will never show up in the Google results without the word "cheater" next to it.
Maybe the RD is too chicken to do his job, but as far as our job I say MISSION ACCOMPLISHED.