Needham’s Charlie Wolf this morning cut his rating on Research In Motion (RIMM) to Underperform from Hold and cut his estimates on the company to reflect the growing threat from explosive sales of the Apple (AAPL) iPhone 3G.

“Sales of Apple’s iPhone 3G appear poised to blow through everyone’s forecasts,” Wolf wrote in a research note this morning. “While RIM’s dominance of the enterprise market appears secure, at least for now, the company’s great growth driver–the consumer market–is bound to come under siege because of the iPhone.”

Wolf notes that the BlackBerry Pearl has allowed the company to “dramatically” increase its consumer sales, but he asserts that the company’s success has stemmed from a lack of competitive offerings.

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