A little food for thought for those think the web is free from Mediapost:

The majority of Google’s 2011 revenue — 96% — came from online advertising, according to WordStream founder and chief technology officer Larry Kim. The No. 1 market generating revenue in Google’s world points to finance and insurance at $4.0 billion, followed by retail and general merchandise at $2.8 billion, and travel and tourism at $2.4 billion.

The top 10 categories also include jobs and education at $2.2 billion; home and garden, $2.1 billion; computers and consumer electronics, $2.0 billion; vehicles, $2.0 billion; internet and telecom, 1.7 billion; business and industrial, $1.6 billion; and occasions and gifts at $1.2 billion.

For example StateFarm spent an estimated $43.7 million on Google AdWords, followed by Progressive at $43.1 million. Amazon.com spent $55.2 million and eBay an estimated $42.8 million. Even Apple spent an estimated $17.9 million on Google AdWords. The infograph lists companies and estimated amounts.

Each market segment also notes commonly used keywords and cost per click for the phrase.

For instance, for the most commonly used phrase under the internet and telecom segment — high speed internet deals — costs an estimated $26.74 per click. Computers and consumer electronics also performs well. The most commonly used keywords for computers and consumer electronics belongs to online video donferencing software at $35.53 per click. Consumers actively searched forr discounts on printer ink cartridges. The keyword phrase ink cartridges discount garnered $26.79.