The corporate market for the Blackberry has reached saturation point. In order to grow revenues Research in Motion has been trying to penetrate the consumer market, however it has come up against formidable competition from Apple's iPhone and Android-based smartphones. Additionally Apple has been making significant inroads into the corporate market. According to Steve Jobs 80% of Fortune 500 companies now use iPhones, and this number is likely to increase with the introduction of iPhone OS 4.0. Basically Blackberry adoption keeps losing momentum. The stock chart of AAPL vs RIMM is very telling:
http://bit.ly/bpM81b