(1) Anonymity to protect the brand
I’m not always sure, if speaking with a single voice was just a way for magazines, newspapers to avoid dependency. The impact of a single journalists on the brand value, in other words the bottom line, is much more obvious, if you know her name. Head hunters or competitors can much more easily find the talent responsible for the lion’s share of opponents success.
(2) Avoiding anonymity to increase personal brand value
With magazines, newspapers cutting costs, it is more than ever in the interest of the individual journalist to be visible in the market and to stay attractive for possible future employers. To have a portfolio of articles you could show is not a bad thing. Some sites already offer journalists the opportunity to show their masterpieces.
(3) Single voice increases brand value
One could also argue, that having one voice is a good thing for a corporate culture which values team work, collaborative approaches instead of stardom of a few extraordinarily talented people. A single voice aka corporate culture might be desirable if you have a publisher which is doing everything to keep you on board.