Why Carl?
There's a number of reasons I believe we're seeing all this 'Carl'. It's a name you can bark out quickly when someone does something stupid, like 'Hey!'. It's just one syllable. See this Mad TV example.
But because of the 'r' and the 'l', you can also whine it out, 'Carrrlll', when you want to demonstrate frustration or disappointment. Like in this Geico ad.
Ultimately, I think it has most to do with the fact that there just aren't a lot of us around anymore, so there's less of a chance of pissing someone off and getting a letter. Let's face it, it's a dying name. Unless you're of a certain age you probably can't name a famous Carl, but we've been making a name for ourselves for a long time in movies, music, science, sports and politics. Maybe it's time for Carl to be cool again!
Does 'Karl' count?
I went back and forth on this and I decided to allow it. Mostly because the 'K' version is pretty rare, plus, it gave me a few more examples. But Karl is less cool than Carl.
I didn't however allow Carlo or Carlos, which are both very cool names. Nor have we addressed the feminine versions, Carly, Carling and Carla but we reserve the right to revisit pending the whims of marketers. Historically, advertisers are very careful not to humiliate or embarrass women, who do most of the buying in this country, and write almost all of the letters.