Originally Posted by ldcdc
You can remove that ability in order to encourage upselling, like easyhostmedia mentioned.
That being said, I would not take away the addon domain feature. It's something that doesn't really cost you anything, and it's quite commonly offered in the industry. Not having it can cost you in terms of sales. I also don't think that the addon domain feature itself is attracting spammers.
The problem we are having is that people sign up with their main domain.
They later add domains to their account to use to spam.
But when we get notified that a customer of ours is spamming and we are provided with the domain being used I usually find that domain in their account as an add-on domain.