Let me begin by acknowledging that everything you're about to read is completely unfair. I cannot possibly have uncovered the five worst mobile websites, because that would require me to have reviewed all of the world's mobile websites, a process that would have rendered me blind, mad, broke, and unable to write this article. There's also the whole question of rampant subjectivity, though I never really let that stand in my way.
But what's really unfair is that I'm about to pick on brands that actually have mobile websites, when what I really should be doing is launching into yet another rant about the actual majority of brands that don't yet have them, vs. the actual majority of mobile users that now have smartphones and are increasingly dependent on the mobile web. Instead I'll confine that rant to this one paragraph, do some deep breathing exercises, then move on to my main rant. Since at least one in seven searches is now conducted on the mobile web, this tidal wave of a usability crisis has been compared to shutting down your business one day a week, and even that grim analogy doesn't factor in consumer annoyance. Having a poor mobile site is inhospitable; not having a mobile site is inexcusable.
In choosing examples of bad mobile experiences, I deliberately excluded (with one glaring exception) brands that offer only their desktop websites on mobile, because that would be like shooting fish in a barrel, and I could only recommend that these bullet-ridden fish carcasses be chucked out and replaced with true mobile sites. I think it's more useful to look at the way that brands are meeting -- or failing to meet -- emerging usability standards for mobile sites, because it's high time we started caring about those standards on behalf of 100 million smartphone users.
To that end, rather than trying to simply expose five bad mobile sites, I looked for sites that were archetypal of certain common mobile usability problems. The sites may be good in other ways, but their usability problems get in the way of users completing their tasks. So being on this list is sort of like coming in last place in an Ugly Dog Contest -- you may have some ugly bits, but you can be sure that at least some of the competition is a whole lot uglier.