I have 2.
1 was mid cata. Husband and wife ran a guild and had an ugly split. I took over raid leading and most of the officer stuff until drama leaked into comms and gchat. Everyone dipped after that.
Another was… mid to end of SL I believe?
The main raiders got a little too high and mighty because of how fast we were clearing heroic. They took “the best players”, aka their little inner circle which we tended to have to carry. And they started a “hardcore mythic raiding guild”. That didn’t last too long 
After 1 season, most of them came back.
2 different guilds on 2 different servers. 1 dissolved and the other I quit during SL shortly after the drama.