Stereotypes in advertising are inevitable. It is relatively impossible to think of a product which does not use a person who would be the one (stereotypically) to use a a product.
For example, women are the ones who typically do housework. Therefore, companies who sell cleaning products cast women in their commercials. One example where a man is portrayed in a cleaning product is Billy Mays and Oxy Clean--which completely speaks against the stereotypical cleaning product commercial.
Products which men are typically seen in are home improvement commercials (like flooring or tools).
As for the negative effects of using people stereotypical to the product, one may be that women simply get sick of seeing commercials which only depict women cleaning (given the commercial supports the thought that women belong in the house cleaning).
A positive effect of stereotyping in commercials would be that a person, regardless of gender, see that others like them (in regards to gender) can "do" something that they did not believe they could themselves.