I finally found something that I can't do on my iPad: Host a webinar. While there are apps in the App Store that allow you to attend a webinar, none currently allow you to host one from your iPad.
But, I did discover a workaround that resolves this limitation plus just about any other conceivable ones: VPN. Using the iPad's virtual private networking (VPN) capabilities, and a handy app downloadable from the App Store, I can control my desktop computer at work from anywhere in the world via my iPad. So, I simply start the webinar on my desktop by remoting in via the iPad. Works great.
So, anything my desktop can do, my iPad can now do. Fabulous!