Media coverage actually seems to be a lagging indicator. There were more articles on Bitcoin from April 9th and seven days after than there were from earlier in that month.
But there definitely is a circular relationship. Higher exchange rate causes more publicity which expands bitcoin to a wider audience or reinforces confidence in the currency causing additional investment, ... which raises the exchange rate further, over and over, until it bubbles and pops.
There is a call for journalists to disclose their position if they hold bitcoins and publish an article.
Trading securities using inside information is illegal in many areas, however what is "inside information" with a decentralized digital currency? Also, would insider trading laws apply to something not a security, commodity, or real currency?