Lots of people are using the internet on their phones these days. Here's a quote from the linked article:
Meeker surmised that the mobile web, which is already expanding during the recession, will explode once the recovery in other sectors of the economy is in full swing. At some point she feels that the mobile web use will dwarf the desktop use of the Internet 10 to 1.
So this means that getting a mobile version of your site up is pretty important right? Look out!

Let's look at the iPhone for a second to see why. People with iPhones use the internet a whole lot more than people with other phones. In fact, it's something like 10 times as much. Here's another impressive stat:
The iPhone comprises 8.2% of all U.S. handsets and 67% of all mobile traffic
Why are we talking about the iPhone again? Well here's the contrast:
- Special mobile websites = the medium adapting to the device
- The iPhone = the device adapting to the medium
And the future is definitely going to be the second option. I know it annoys the hell out of me when I get redirected to a "mobile" site on my 3GS, I always feel like I'm missing out on something.
When they can do it without compromising, people love using the net on their phones. Otherwise, forget about it.
So relax, stick to making your site kick ass in other ways, and save the mobile budget for something else. There are plenty of cool things you can do that aren't a just a special version of your site. Like a new way for people to check in at the airport for example. Because soon, the distinction between "mobile" and "non-mobile" will disappear.