The current mortgage crunch hitting the stock market could have implications for the online advertising market as well.

According to Media Biz, the fourth-biggest spender of online advertising for the month of July was the now-troubled mortgage lender Countrywide Financial, which Nielsen//NetRatings says spent $34.8 million. The top online advertising buyer for July was mortgage information site Low Rate Source, spending $46.3 million.

With talk of Countrywide declaring bankruptcy, La Monica admonishes users of an out-of-the-blue revenue warning from Yahoo, due to a weakness in auto and financial services ad spending.