In 2007 Research In Motion’s BlackBerry platform owned the mobile enterprise market. As the iPhone – and Google’s Android platform after it – have grown in popularity, RIM has steadily lost market share. With the help of a few bad business decisions and some products that did not live up to their potential, RIM has reached the point where they are in significant trouble as a company.

Now it looks like they’re about to suffer another blow. AppleInsider has apparently gotten hold of an internal memo detailing plans by energy giant Halliburton to transition from BlackBerry to iOS as its mobile business platform. According to the document, the company intends to expand its use of mobile technology in the coming months as it phases out BlackBerry and phases in the iPhone. The decision apparently comes after extensive research into the mobile platform options available – iOS, Android, and BlackBerry. The company concluded that iOS best suited Halliburton’s security and control needs. The company plans to make the transition to iOS products over the next two years.

The loss of such a large customer could do significant damage to the already struggling RIM. The company has made some efforts in recent months – including appointing a new CEO – but it remains to be seen whether it will be possible to right RIM’s ship, or whether the recent efforts are too little, too late.