Salesforce.com's shares spiked last month amid reports from Bloomberg that an unspecified company was in talks to buy the Software-as-a-Service firm. There was a repeat earlier this month when Bloomberg reported that Microsoft was evaluating a bid for the firm, but had not started talks. CNBC is now reporting that talks between the companies have, in fact taken place, but that they've also come to an end with no agreement being reached.

According to "multiple people familiar with the situation," Microsoft was offering around $55 billion for the cloud company. Salesforce's founder and CEO Marc Benioff wanted to push the price higher still, apparently as high as $70 billion. CNBC's sources claimed that Microsoft CEO Satya Nadella was hesitant to commit to a deal with such a high price and impact on Microsoft.

Even at $55 billion, the acquisition would have been Microsoft's largest by far. The company's biggest purchase to date was $8.5 billion on Skype in 2011, with the Nokia devices unit, bought in 2013, coming in at second place at $7.2 billion. The previous record holder, the $6.3 billion purchase of aQuantive in 2007, was disastrous. Five years after that takeover, Microsoft had to write down almost the entire purchase price.

Buying Salesforce would have dwarfed these deals, but it seems that no deal is likely to materialize. Talks were concluded in early May, CNBC's sources say, and there are no plans to resume them.