I have no idea which forum this should go in . . .
I have a lot of show-business books, dating from the mid-1800s up through current-day. The abbreviation for “microphone” has always been “mike,” up till a few years ago, when many people (and magazines, including my own) began to change it to “mic.”
WTF? Why? how? Whaaaa? I keep seeing it as being pronounced “mick.” Any amatuer Williams Safire out there can give me some help on this change?
Well you’ve got me totally boggled because I’ve always seen it written as ‘mic’ and lately I’ve been wondering why I keep seeing it written as ‘mike’.
Hmmm…Webster seems to agree with you though. ‘Mike’ is listed as an abbreviation for Microphone originating in 1924. ‘Mic’ has no relevant listing. I guess this is just a current example of the evolution of our language. Enjoy 
My WAG is that when you go plug your microphone into a sound mixer or amplifier, the input you are looking for says “mic” (or, like my computer, has a little icon). That’s my guess as to how the abbreviation crept into usage. “Mike” is 33% longer to write in little tiny letters on a label.
In normal written form, though, I prefer the standard. I like mike.
There’s a colloquial word that you say when someone has been particularly gullible. I saw it once written as “sike”, but fortunately, it has all but been replaced by “pysch”.
Probably because mike doesn’t make a lot of sense as an abbreviation, but mic does, at least to me. This is the first time I’ve ever seen it written as “mike”, but all sources indicate this is the correct usage. Probably it is being used since the high school stage crew entering the profession doesn’t know any better now, but that’s just a WAG.
I guess this is an odd example of a word evolving to be actually more similar to its root, instead of more different.