Saw an analysis the other day that boiled down to:
Site with ads: 5.5mb
Same site without ads: 50k
Yes, 90% of the bandwidth was used by ads. This was for some major newspaper or magazine on the order of Business Week, not a site that exists solely to serve content-free advertising.
How is this fair to people who pay by the byte? I've seen phone data usage rates as high as $100/GB!!! and even if you're paying a more reasonable $5 or $10 per GB... it adds up fast. I've found that just for ordinary browsing on my PC, I can easily use as much as 1GB/day even without visiting YouTube.
Methinks it's time to start metering and billing advertisers who consume bandwidth that users have to pay for. Surely someone can code a phone app to do this.