No, bud does not necessarily need to be cooked in order to get high from eating it.

What heating does is speed up a process known as decarboxylization in which the THC molecule loses the carboxyl group (COOH) that it is bound to, this is the same process that happens when bud is dried cured. You'll also notice that most recipes with marijuana also involve something with a high fat/oil content, because thc is fat-soluable and supposedly it makes it easier for the cannaboids to pass through the GI tract into the bloodstream. Though cooking is not necessary, it is more effecient. If you eat an 8th of good quality raw bud you will likely get pretty stoned, but if you cooked with it perhaps the onset would have been faster, and more than one person could have enjoyed it.