“Too good to check” means that a sensationalist story has come from one source, and the urge is to publish the story and to credit that source—it’s “too good to check” other sources and facts, only to find out that the story has dubious merit. “This story was too good to check up on for veracity…We give it as it came, via an anonymous telephone tipster” was cited in print in 1945. “Too good to check” became a standard journalistic expression by the 1980s.
 
 
26 October 1945, Boston (MA) Herald, “Rod and Gun” by Henry Moore, pg. 42, col. 2:
This story was too good to check up on for veracity…We give it as it came, via an anonymous telephone tipster.
 
19 June 1972, Winnipeg (Manitoba) Free Press, “The Shetland Islands” by Claire Street, pg. 7, col. 3:
It was too good a story to believe, really—but much too good to check in case it proved imagination—that we heard last week about the oil men down at the Sumburgh Hotel ba one night ...
 
Google Books
The Hour:
A Novel
By Ron Nessen
New York, NY: Morrow
1984
Pg. 257:
You ever hear that newsroom expression ‘Too good to check’?”
 
Google Books
American Politicians and Journalists
By Charles Press and Kenneth VerBurg
Glenview, IL: Scott, Foresman
1988
Pg. 89:
A reporter once told us half jokingly when we asked if a story about a politician was really true: “that’s the kind of story that’s too good to check out.”
 
3-5 August 1990, USA Weekend, “Who’s on first (so to speak)?”, pg. 6, col. 1:
It’s one of those stories almost too good too check.
 
New York (NY) Times
Propaganda Blitz
Published: September 08, 1991
To the Editor:
Elaine Shannon claims in her review (July 28) that our new book, “Cocaine Politics: Drugs, Armies, and the CIA in Central America,” is loaded with stories “too good to check,” from sources, usually crooks, whose credibility we made “virtually no effort” to assess. These charges would be devastating if true, but where are her examples?
(...)
PETER DALE SCOTT JONATHAN MARSHALL Berkeley, Calif.
 
Google Books
The Fiddler in the Subway:
The Story of the World-Class Violinist Who Played for Handouts…and Other Virtuoso Performances by America’s Foremost Feature Writer
By Gene Weingarten
New York, NY: Simon & Schuster
2010
Pg. 72:
There is a maxim in journalism that some stories are just too good to check out. What that means is that the juiciest of tips, when subjected to research, tend to desiccate and crumble.
 
Hot Air
Too good to check: Romney leading among Hispanics in Florida?
POSTED AT 2:31 PM ON OCTOBER 13, 2012 BY ED MORRISSEY
Could Mitt Romney be riding a preference cascade in Florida that includes Hispanic voters?  A new survey shows Barack Obama’s support rapidly eroding in a key Democratic constituency — and this isn’t a Republican internal poll, either: ...
 
MSNBC—Hardball with Chris Matthews
Too good to check? Breitbart runs with fake Krugman bankruptcy story
Maryalice Aymong
7:19 PM on 03/11/2013
Think of the last person you might expect to be filing for personal bankruptcy. Here’s an idea: economist and New York Times columnist Paul Krugman. The man won a Nobel Prize for Economics!