Product placement is a
bad, bad thing. It was pioneered by crappy
1950's TV shows (cue countless 90's parodies along the lines of "
Captain Indestructible saves the world again, and has time to smoke a
sweet, sweet, refreshing Laramie cigarette") as an unsubtle extension of sponsorship. It was elevated to an artform by Hollywood films from about the late 1970's onwards, where corporations were prepared to stump up big bucks to get their
logo on screen, and preferably have their product become integral to the plot.
If you want to see large amounts of product placement, check out the Back to the Future series, E.T., Mac & Me, Inspector Gadget (notice how many of these films are aimed at kids... hmm).
FedEx seem to throw a bundle of notes (which arrive overnight no doubt ... :) to a studio every year to get themselves heavy product placement in a Summer movie : two that I can remember were Runaway Bride and that thing where Tom Hanks crashes a plane (the trailer for which contains their logo and livery in nearly every shot).
It should also be noted that although Wayne's World "spoofed" product placement, they obviously got paid for all the product placement in that scene. Pretty crafty eh? And Austin Powers 2 makes it abundantly clear what Mike Myers's real views on product placement are (i.e. "more of it please!").