With proper guidance and care in respect of health and education, involving in television advertisement as child can't be harmful. This way the child acquires experience and the self confidence to build a future with it as a career, i.e. he/she is interested in it with the talent and the capability. But for this, the child and the parents need to take right choice when required and most importantly, the parents or the guardian, under whose guidance the child works, should take care that the child isn't overburdened with stress.
Children, with their parents' permission, have the right to be involved in television advertising as long as child labor laws are enforced. Yes, some products are sold to children even though they could be for older adults. Yes, there is a commercial and advertising blitz that assaults the sensibilities of Americans everyday. However, it is a free market economy and advertisers can use whatever means necessary to sell their wares, within reason.
I believe that children should not be involved in television advertising. Advertising that uses children is just exploiting them. Children should not be able to make a lot of money at such a young age, which is what many children who act do. They are robbed of their childhood and can end up in getting in disputes with their parents about their sudden wealth.