In a merger of this scale, IBM would need to take a hard look not only at Sun's finances but also at any antitrust issues that may arise, as well as potential conflicts related to intellectual property. Those could include compatibility of software licenses and patent agreements with third parties.

"In a deal of this size, there are typically lots of moving parts," said Randall Bowen, an attorney at Grad, Logan and Klewans in Falls Church, Virginia. "Think of a kaleidoscope, where you turn it and everything comes together to form a nice symmetrical shape. Either that happens and everything falls into place, or else it shatters."

The Wall Street Journal reported last Friday that IBM was scouring Sun's business contracts for potential conflicts in a prelude to a possible merger, a process it said was expected to take "a number of days." With another week over and no word about a deal from the companies, some observers are starting to wonder if there's a holdup.

"It's impossible to know what it is they're looking at, but the fact that it's taking this long gives one pause to wonder whether there's just such a volume of contracts to look at that it's occupying all this time, or whether they've found some issues that they're busily chasing down," said Steven Frank, a partner with the law firm Goodwin Procter.

To be sure, the due diligence process for a merger this size could take months to complete. But companies often do a cursory review of the business they hope to acquire in order to announce a preliminary merger agreement. They then take several months before the deal is finalized to pore over the details.