With the economy struggling, analysts say that some corporations are starting to tap so-called revolving lines of credit and other forms of backstop financing that could lead to banks being forcing them to raise money to cover the loans, the New York Times reported today. Collectively, banks have pledged to lend companies more than $1 trillion. And because most of those loans have not been made yet, and many perhaps never will be, the banks have not accounted for them on their balance sheets. Some companies, such as Univision, Porsche, CIT Group and Sprint Nextel, have already tapped lines of credit in recent months. A growing number of companies might soon follow suit, analysts say.