All the frikkin time!Have you ever seen a player refuse to share plot-relevant information? Like, their PC is the only one who witnessed the thing, the next phase of the campaign assumes that the party acts on that information, but the PC chooses to sit on the info? Is it a mistake on a GM's part to give that kind of insight to a single player rather than the whole group, or is it good form for a player to share knowledge?
Comic for illustrative purposes.
Often the information isn't "given" so much as the PC is the only one present and/or the instigator who ferrets it out (like opening the safe when others aren't watching and handing over the treasure, but keeping the diary and map).
Whether or not it's good form depends on the campaign style. I tend to think stuff like that should generally be shared widely and quickly (if for no other reason so more than one memory can be dredge the fact up when it is relevant). Some campaigns are expected to have secrets though. It's hard to fault someone from keeping a secret when that is an expectation.