U-M issued the following notice to the media

As many alternate uniforms as Michigan's football and basketball teams wear these days, there's at least as many iterations of the famous block "M" floating around.
At The Oakland Press, we recently received a politely-crafted letter from U-M Public & Media Relations requesting we use just the two latest versions of the famed insignia. The notice also asks that "we," assuming this is a standard letter sent to all local media, remove any of the offending versions from our archives.

Not a "blocked "M"

"One of the goals of the athletic department is to create brand consistency by clearly defining and limiting versions of the block M that so distinctly represent our institution."
 That's an interesting justification coming on the heels of the ever-changing uniforms that have found their way into the Wolverines' locker rooms of late.
We try to use the latest versions on logos, but it's strange a program which is constantly changing it's look is insisting media stick to two of its logos.
For a quick history of the evolving block "M" and other University of Michigan logos from the past, visit SportsLogos.net.