This and this and much more give a strong indication of where online (and offline?) business models are headed. (Give me a C, give me a P, give me a C.....aaaaaaand what do we have?) And while I have nothing against advertisements (I did sing ad jingles on school trips. Doodh, anyone?), it does make me wonder: Whatever happened to the good old pay-for-what-you-need concept?
Being ad-supported is definitely a safe bet for an early-stage service trying to reach critical mass. But surely, there must be enough users willing to pay for value adding services they use frequently. We do have folks like Flickr, Netflix or Amie Street who monetize the Web (1.0/2.0) without relying solely on ads. I will *not* pay to be poked on Facebook, but I am willing to pay for things I use for my research or finding the closest Macys :). And I'd rather pay $5 than click on 25 annoying ads. Not to mention (shudder) pop-ups. Heck, I might even pay Facebook to avoid something like this (NSFW).
My grudge with being entirely ad-supported is the conflict of interests it creates. The primary motivation for the service is maximizing ad-revenue. So the model pushes the business towards optimizing the service for advertisers, shifting focus from user experience. The designers are asking "Where do the ads go?" before (and more frequently) than "Where does the content go?", and that's when you get pages like this. Or brilliant ideas like Beacon.
Through one channel or other, you are going to pay, because the service has to make money. The choice is between pay-for-what-you-need or be-assailed-by-annoying-ads-and-buy-stuff-online for what you need.
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Sources: Techcrunch, cnet, (my beloved) Valleywag, Lorelle VanFossen.