This requires you to waste your life monitoring your allies. Not to mention the lag in the servers. By the time you've been informed your allies have been bought, they will already have attacked you and taken all your gold.
Some people will also buy your allies before they attack, so they can get more per hit, and not have to wait for regen
There are more efficient ways to deal with them. If your in a clan, your clan with pin them. If you have friends who can help, ask them to.
This is a part of the game??? Correct me if I'm wrong but this is just a tactic to earn money, you can't complain about this in a war game