[ariwilson]

There can be both a finite appetite for advertising and increasing Google revenue as long as Google is either making advertising more effective (expanding the market), taking revenue from other publishers (controlling the market), or making money outside of advertising.

Some random stats I found estimate that advertising is currently a $500B yearly industry, which means Google is only 15% of the industry.

[em500]

Right, I found estimates of $600B yearly ad spend. To put that into context, total annual spending (aka world GDP) is over $70T, meaning that less that 1% of all spending in the world is on advertising.

[adventured]

And you can probably slap another one or two dozen trillion dollars onto that surface GDP figure. The underground / black market economy is very, very substantial.

[MarkMc]

In addition, the online advertising market is growing naturally as more people get connected to the internet and already-connected people get wealthier. This is why Facebook is so keen to dominate the Indian market that they are willing to offer free (but not net neutral) internet access.

[runeks]

You forgot the most important part: making ads more targeted. More more targeted an ad is, the more you can charge for it. So Google can sell the same number of ads to the same number of advertisers and yet make more money, while advertisers get more bang for their buck.

[semi-extrinsic]

Only 15%, but then they don't do TV, radio, magazine, newspaper or billboard ads.