Hat: Good point about the differences between simply passing on info and making sure that info is accurate. I'd make the case, though, that the most important thing a reporter can do is ensure accuracy whenever possible, even in sports journalism, philosophically speaking. Plus, I just hate it when the sports media build up groundless stories, as they are known to do.
You bring up an interesting point as well, and it's one that causes a good deal of knuckle-cracking for those of us who have access to info (the scale of which is unimportant...it's the same type of scenario for both local and national guys). The problem is that if it's a reasonably reliable source, you've got to go with it, even if you personally find it questionable or unlikely. If you don't, the source might get insulted that you didn't use his info, and will seek out someone else in the future. If this is a decent source, you sure don't want to have him doing that.
Kind of a double-edge sword to be sure. On the one hand, much of this grapevine material doesn't ever materialize, which causes readers, viewers or listeners to label you an idiot. Nevertheless, when the scoop does come down, you've got to have it before anyone else if you're doing your job.
I've learned over the years that a large number of fans choose only to remember the mistakes and conveniently forget the items you got right...and got first. Goes with the turf.