I just believe beat reporters who are closer to the pulse of the team they cover than anyone else on the internet. So my personal opinions of guys like Alex Speier, Pete Abraham, Rob Bradford, John Tomase, Peter Gammons, etc. aren't a factor. Same with a national guy like Ken Rosenthal, who is always working and knows everybody. Whether you like him or not, he's more credible than most.
You're right, there are no reliable sources. It's arguable the very term is a misnomer; otherwise, why is someone afraid his name will be used? It's not like any of these reporters, team employees and player agents are at risk of having to go into the witness protection program... or are they? Some may risk their jobs, whether through being fired for spilling the beans, blackballed for breaking trust and thus, losing future scoops, or just from fabricating or feeding misinformation campaigns (oops, that's ok with half the country these days). Some are certainly being used as pawns by both sides of management and labor, but that comes with the badge...