17. Concentrations

Concentrations of Credit and Business Risk

Financial instruments that potentially subject us to a concentration of credit risk consist of cash and cash equivalents, marketable securities and accounts receivable.

At December 31, 2015, our cash and cash equivalents and marketable securities were maintained primarily with six major U.S. financial institutions and three foreign banks. We also have used three Internet payment processors in both periods. Deposits with these institutions at times exceed the federally insured limits, which potentially subject us to concentration of credit risk. We have not experienced any losses related to these balances and believe that there is minimal risk.

A substantial portion of our advertising revenue is generated through arrangements with one advertising network partner. We may not be successful in renewing any of these agreements, or if they are renewed, they may not be on terms as favorable as current agreements. We may not be successful in renewing our agreements with advertising network partners on commercially acceptable terms.

The percentage of revenue generated through advertising network partners representing more than 10% of consolidated revenue is as follows:


	Year ended December 31,
	2015		2014		2013
Google	36	%	50	%	56	%

Advertising network partners comprising more than 10% of the consolidated accounts receivable balance was as follows:

Year ended December 31,

Google, Inc.