The recent surfacing of the baseball offseason's dumbest rumor -- the Giants interested in Jack Cust -- prompts me to clue those of you not in the media business as to how many of these rumors get started. Consider it a public-service announcement.Let's take the Cust rumor as an example, since it's comically front and center. If you know even the tiniest little thing about the Giants and Cust, you know how ridiculous this notion really is. Cust simply doesn't fit. He's a liability on defense at best, which is why he's a designated hitter. The Giants play in the National League. Rumor squashed.But this kind of rumor gets out there all the time, given legs by a national baseball writer for a fairly well-respected website, and this is likely how:Phone rings. National writer picks up.Agent: "Hey, it's me. Remember when I helped you break that story last June?"National writer: "Yeah. My boss loved it. What's up?"Agent: "I need you to return the favor."National writer: "Sure. What's up?"Agent: "My guy's not getting a ton of interest out there. In fact, I've got one, maybe two teams in on him, tops. I need to create some buzz. Make people think he's in higher demand."National writer: "OK. Who have you talked to?"Agent: "Well, I called the Giants, Phillies and Yankees, but they're not into my guy at all."National writer: "But you talked to them, right?"Agent: "Well, yeah. But only for about 10 seconds. They laughed and asked about one of my other guys."National writer: "But you did talk to them, right?"Agent: "Technically, yeah."National writer: "Perfect. I'll write a little something saying the Giants, Phillies and Yankees recently spoke with the guy's agent. It's not untrue."Agent: "No, it's not. It's perfect. All I need is a couple more teams' names out there attached to my guy. Now the teams who do like him might think they need to bump up their offer. Thanks."National writer: "No problem. But now you have to let me break the news when your guy really signs."Agent: "No problem. You'll be the first to know."Pretty shaky, right? Totally. But that kind of crap happens all the time. So the next time you see something like the Giants are interested in Cust, think of what you just learned and move on with your day.