YES, you need mobile.
WHY?...here are some facts.
Currently 1/3 of humankind has mobile internet access, which is twice as many as the number of internet-connected PCs.
50% of the world's population is expected to have access to the Internet through a mobile device in 3 years! Mobile advertising spending in the US is projected to surpass $7.5 billion by 2013.
Today, there are about 2 billion users of SMS text messaging worldwide. According to industry studies, over 80% of the cell phone users are willing to receive opt-in text messages.
Mobile has a low entrance cost and an ROI that is limited only by creativity and drive.