Advertising agencies contain specialists in marketing, advertising creation and media analysis and placement. Large companies, with budgets in the millions, almost always use advertising agencies, often more than one. In popular culture, ad people are often stereotyped as hucksters, but sober marketing types at the nation's most conservative companies choose advertising agencies with straight faces. What do they see in ad agencies? They see smart professionals who, at their best, know how to connect to an audience and persuade them to buy.