A small subset of the Blogging community would be good with marketing, but not everyone.
And for the same purpose there is are plenty of PR firms that specialize in advertising online and in the social networking world (not just ads, but designing virals campaigns etc)... and they have much better contacts all around and the ability for you to expand outward from online advertising and marketing to other's easily as well (TV/Radio/Billboard/etc)
Well, I would say that the valid conclusion from the arguments is that Sales Dept should have a blogger. Whether a new hire, or current staff who starts testing the water part-time, or whatever.
And for the same purpose there is are plenty of PR firms that specialize in advertising online and in the social networking world (not just ads, but designing virals campaigns etc)... and they have much better contacts all around and the ability for you to expand outward from online advertising and marketing to other's easily as well (TV/Radio/Billboard/etc)