Having an understanding of your subject would be very good, for example, a background in Sociology. This pips your basic interest in the subject first, photography is a way to express the photographer's feelings.
for me, there are 2 basic "requirements" for being a good photographer
2) "having something to say"
my friend once (or more than once) said "if the picture tells nothing, don't click the shutter"
to be a "professional photographer" you just need good marketting
According to the topic....from what i feel.....seems like its true. At least you need some form of qualification to get somewhere....if not it will mean im wasting my time and money getting a diploma at a art school now...haaa.
personally, IMHO, don't think you need any qualifications to be a pro photog lor. it's the quality of your pictures that counts, really. you can have all the papers in the world and if you can't produce a decent pix, it's all useless. unless you're looking for a photo journalist position or something similar, then mabbe.
certification is just to arm you with the basics, then you gotta prove yourself, more so with arts and photog. end of the day, if someone stops to admire your picture, then you're ready.