My alliance has had members who've had to use vacation mode for different reasons. Either because their busy with school and find logging in every day a risk of getting distracted, players who've been travelling in areas where it's expensive or difficult to use the Internet. I've also had members who've used VM as a tool to figure out if they wanna keep playing or not.
For some alliances it's easy to defend these inactives or to just kick them out. But for other alliances where the members are valuable players and actual friends it's not as easy to do so. Neither the alliance nor the player should be punished because said player can't play during a period. Neither should they be punished because other players misuse the tool.
Either way, most peoples who misuse VM either end up doing themselves or their alliance a disservice anyway. I feel the VM gives more than it takes out of this game and I'd honestly not like it to be removed.