Not so fast there friend...
I've always carried at least one spare tube along with a patch kit. The spare tube has allowed me recover from a flat and continue my ride home on numerous occasions; I don't recall that I've ever had to resort to my patch kit... However, one day I had a sidewall fail, and my lack of preparedness was rewarded with a 5 mile walk home. Ever since then, I've always carried a spare folding tire as well. That was before I learned about the dollar bill trick, so that's my backup if I fail two tires in one trip
In the interest of full disclosure, the bikes I commute on (all my bikes, for that matter) are road bikes, but I try to make reasonable choices for tires, e.g. 28mm cross-section, kevlar belt, mostly. The one that failed the sidewall happened to be a standard Pasela, not that a kevlar belt would have saved the sidewall.