I fully disagree with arguments here given against plausible deniability.
First, plausible deniability doesn't apply just to whole encrypted DISKS and PARTITIONS but also to encrypted FILES (with encrypted hidden VOLUMES), for example in TrueCrypt. Using encrypted disks or partitions has no significant advantage against single files/volumes, for example the presence of a very suspicious encrypted partition is easily detectable and an investigator/attacker examining your PC can easily determine that you KNOW and LIKELY USE encryption tools such as LUKS or TrueCrypt.
So the answer "I securely erased that disk/partition, no cryptography here" is no more believable than saying "that TrueCrypt file doesn't contain an hidden volume, because I don't need that added security. The proof? Look at the contents, they are confidential but not critical nor illegal, here is the password".
Second, if you are asked for a password and you answer "I forgot my crypto key" you appear as a NON-COOPERATIVE suspect whereas if you give one you can't be accused of that and the whole burden of the charge of lying is on the investigator/attacker.
Moreover, how much is credible that you FORGOT a password on a BIG crypted file or on A DOZEN of crypted files that you still KEEP on your computer?
Plausible deniability is even more important if you live in a "democratic" country, where you can't be forced to provide a password: by giving an (harmless) password you can't be accused of lack of cooperation with the investigators, on the contrary if you don't give it you appear less credible and more suspicious.
Third, there are countries, like UK, where the judge can keep you in JAIL for a long time if you don't give him ONE password. Again, with plausible deniability you can give him the "harmless" password and you can't be charged of impeding the justice and jailed.
Fourth, if you have plausible deniability you can always CHOOSE to assert that no hidden information does exist and no second password does exist OR (for example if you are waterborded) admitting they exist and give them the second and "true" password. Plausible deniability gives you ONE MORE CHOICE that you can't have without.
My frank opinion: the opposition to plausible deniability is likely given by the long-time opposition a lot of Linux supporters did against TrueCrypt, that was done just for license issues albeit disguised for technical reasons.
An easy-to-use and effective plausible deniability is likely the best feature in TrueCrypt but a lot of Linux users, which didn't find TC in their distribution, get used to crypt with tools without it (for many years LUKS had no plausible deniability support) and get used to say that "plausible deniability is worthless or harmful".
It was a case of "sour grapes" that still goes on.
And I find really disconcerting that a cryptsetup\LUKS developer, after the usual trite statements about plausible deniability, refuses to give any information, in a FAQ!, about the implementation of plausible deniability in that tool. Huge lack of professionalism here.
My STRONG advice: USE PLAUSIBLE DENIABILITY (especially with hidden volumes), better with a proven tool such as TrueCrypt 7.1a (look carefully at its successors, like VeraCrypt or Ciphershed, but don't use them until they are PLAUSIBLY audited!).