its not something we can control.
If you are referring to the fact that should people wish, they are able to create alternate accounts, then yes. It is possible then to use those accounts to create multiple threads for each of your domains, though it will be a hassle, taking too much time and effort, also being incredibly conspicuous. The whole reason for creating multiple accounts would be to put many domains on offer at the same time, though it would arouse suspicion if a large number of newbie accounts were to begin creating threads for domains.
It is also probable that should one account be detected as being an alt, the user would face the risk of a ban, which would result in the banning of all the other accounts (lest you use proxies which would take a lot of effort). The rules apply to individuals, not accounts (AFAIK, since there was a precedent when an individual used multiple accounts to bump a thread, which violated the rules) and hence if this behavior is noticed, then the person would be banned.
The rule is fine. It prevents clutter and allows for equal advertising opportunity.