The most flagrant criticism of the royal family by far has come from a single mysterious person named Mujtahidd. (The word means “studious.”) Starting late last year, Mujtahidd began posting sensational and richly detailed accusations about corrupt arms deals, construction boondoggles and back-room power plays involving numerous royals, including King Abdullah. He often writes directly to the Twitter accounts of the alleged malefactors.

“Is it true that your house in Jedda cost $1 billion but you charged $6 billion and pocketed the rest?” he wrote early this year to Prince Abdul Aziz bin Fahd, one of his favorite targets. There is no way to verify any of his claims, but the royal family clearly takes him seriously, writing heated denials. He now has more than 660,000 followers.

The royal family is said to have made strenuous efforts to uncover Mujtahidd’s identity, to no avail. He is widely rumored to be an alienated member of the royal family, or someone relaying information from such insiders.

In the meantime, Mujtahidd appears to have emboldened many other Saudis.

The annual National Day holiday last month, for instance, elicited a gale of criticism. On the day before the holiday, the interior minister, Prince Ahmed bin Abdul Aziz, released a statement noting that “we enjoy a luxurious lifestyle.” The statement was meant to be patriotic.

But on Twitter, many Saudis said they saw the prince’s “we” as an arrogant reference to the royal family, not the nation. The minister, upset, posted a defense. That drew more angry denunciations, including the following: “Remember that we have no medical insurance, no jobs. Prince Salman” — Prince Salman bin Abdulaziz al-Saud, the heir apparent — “has billions of dollars, and don’t forget all the fenced-in lands belonging to the royal family.”

The insurgent emotions visible on Twitter appear to have carried over into the traditional media, where columnists and talk show hosts have become more assertive in criticizing the government. But Twitter still drives the conversation.

The new voices are not confined to calls for Western-style liberal reform. The largest Twitter followings belong to clerics. Muhammad al-Arifi, a conservative cleric, has more than 2.7 million followers, dwarfing the most prominent champions of women’s rights, for instance, and members of the royal family.