I asked Twitter. What makes a logo designer a professional logo designer?

If people pay you to make logos and are satisfied, you are a professional logo designer. It's no different than any other craft. For other organizations, I've designed one logo so far ( http://www.703designs.com/portfolio-logos ) but I wouldn't consider myself a logo designer until I've made maybe ten quality logos outside of my own ventures.

All very nice, but it's all just buying into the general twisting of the word "professional".

The Wikipedia definition is much closer:

A professional is a person in a profession that requires certain types of skilled work requiring formal training or education. In western nations, such as the United States, the term commonly describes highly educated, mostly salaried workers, who enjoy considerable work autonomy, economic security, a comfortable salary, and are commonly engaged in creative and intellectually challenging work

The essential part is the autonomy, which comes from responsibility. You wouldn't give someone you hire autonomy unless they are a professional - i.e. they take responsibility for their work and for the outcome of their work.

A bricklayer's assistant might be paid for their work, but they're not a "professional". In fact, even a bricklayer isn't really a professional, because he will pass on the responsibility to the person who tells him to build the wall. At the top of that chain of responsibility you have an architect, who stakes his personal reputation on the successful completion of the project. That one is a professional.

Other examples of professionals: lawyers, doctors, entrepreneurs, managers (both mid-level and senior - but I'll grant you that many managers are awful professionals). Basically, anyone who, if things go wrong within the piece of work they have control over, will get royally fucked.

I had the pleasant experience of suggesting a 'Made with Lisp' logo to comp.lang.lisp in 2006, and suddenly 5 popular logos (like the Lisp lizard) were designed and posted to the web. All because of my small suggestion.

Ugh oh .. is "I asked Twitter" are going to be new "Top 10" lists ? It's a same concept really.

I think nobody cares about your logo. Unless it is either an anus or the Lacoste crocodile (a case in which the logo really helps sell merchandise) it won't make a big difference. Make it one of those details you'll spend a couple of hours on after you're burned out from hacking.

A senior designer / creative director should take into consideration brand strategy, market demographics, messaging, product positioning, company culture, etc.

A designer makes stuff look pretty.

I'd say vectoring is a big part of it.