Lately, they really make you *work* to get low-cost clicks. The complex quality-based bidding formula is not entirely profit-oriented, but some of the reason they’ve been so profitable during an economic downturn is because they’ve managed to squeeze higher prices out of the “low priced” keyword inventory. They’ve taken aim at “lowball bidders” in some categories, and made it harder to bid low, plain and simple. Either you pay more than you used to pay, or your ad doesn’t show up.
People who’ve been neglecting paid search trends also don’t realize all the amazing free and low cost tools that are now available to improve your ability to build, adjust, and refine campaigns on the fly. New advertisers look at the old paradigms (large keyword lists, lowball bids, bid management to ROI) and don’t see that the game truly is about relevancy today. Careful attention to user intent, and providing “scent” right through the buying process, is a big part of what drives successful campaigns.
That pretty much sums it up for the difference between 2005 and 2008.