Anonymous sources are not anonymous to the press, who usually require at least two independent sources for any given assertion - at least, those news organs that wish to be taken seriously over the long term do. Journalistic anonymity can be used abusively to manipulate the news, but then so can official stonewalling and censure of outspoken individuals.
What's the point of having the source maintain anonymity for "normal" non-secret stuff? There's no point in not naming your source unless it's damaging secret stuff--in which case call your source "anonymous" instead of "a senior administration official" or "party staffers".
For anything else, if your sources remain unnamed, there's no way for the public to corroborate your assertions, and it's not "news" anymore, it's "opinion"...
