funny you ask this as I have been walking around a lot with my 70-200 and not bothering to take any other lens with me and using my iphone as my wide angle camera. Seems to work for me, IQ is on par with just about any other mid range PS out there plus it has the advantage of being very light and something Id take with me anyway. It also is the best PS on the market for taking the photograph, doing some quick pp through snapseed and off to my facebook or flickr accounts. But if that doesn't work for you I'd invest in the 17-55 f2.8 IS over any of the wide to normal primes especially on APS C. Its way more flexible and you don't lose much if anything in the IQ department. My 17-55 was glued to my 7d.
Now that's just crazy talk right there! Kudos to you sir for keeping things in proper perspective!
If you're taking photos with facebook or flickr as the only location of the end-product, you don't need a DSLR.
...you see I was simply comparing an iphone to a mid range PS and noting the benefits that you can fire it off to facebook or flickr with the swipe of a finger. Different strokes for different folks, I enjoy the portability of the iphone and not carrying around a bag full of lenses. I know this may be sacrilegious to some but sometimes I don't even bring a camera on an outing as I enjoy the company of my wife and kids a lot more than taking photos