Again, as long as working and/or owning a company is legal at whatever age you are - that's wonderful. Otherwise, it is just like any other illegal activity, and people will do it until they get caught. In the case of kiddie hosts it is at the expense of people who are their clients usually.

There are certain restrictions though, for example a person under the age of 18 cannot legally enter a contract without parental signature. This means there is no TOS, no Privacy policy etc which is necessary for protection of the business and the customers.