Saudi officials revealed on Tuesday that they had detained leading blogger Fouad al-Farhan. BBC Middle East analyst Roger Hardy looks at the influence and aims of the country's more than 500 bloggers.
They blog to give voice to their thirst for change - or just to escape isolation and boredom.
A campaign in underway to press for Farhan's release
The blogging boom of the last two or three years has given young Saudis a new means of self-expression in a hitherto closed society.
One of the best known is Fouad al-Farhan, who is 32 and runs a small IT company in Jeddah.
Unusually, he blogs under his real name.
Freedom and Islam
At the top of his Arabic blog is the slogan: "Searching for freedom, dignity, justice, equality, public participation and the other lost Islamic values."
As those words suggest, Farhan is no secularist. For him, there is no contradiction between freedom and Islam.
His blog (http://www.alfarhan.org/) deals with corruption and the plight of political prisoners.
He has now become the first Saudi blogger to be arrested.
The Saudi authorities have not disclosed why he is being held, other than to say that he is being questioned for "violating non-security regulations".
But it looks as if his detention results from his open support for a group of reformists who were arrested last year and are being held without charge or trial.
The authorities have linked them to terrorism, but their supporters are convinced they are being punished for their political activity.
Young Saudis chafe at the many restrictions they face... They use their blogs to attack the religious police - or just gossip about fashion, travel and relationships
Blogging really took off in Saudi Arabia in 2005.
Now there are at least 500 or 600 Saudi bloggers, both men and women, using either English or Arabic.
In the past bloggers have sometimes been warned off and occasionally shut down.
One outspoken woman, who blogged under the name Saudi Eve, found her site blocked after she wrote freely about sex and religion.
Cyberspace has become the new battleground in which liberals and conservatives confront one another.
Young Saudis chafe at the many restrictions they face in a country under the sway of an austere form of Islam.
They use their blogs to attack the religious police - or just gossip about fashion, travel and relationships.
Religious conservatives see themselves as the defenders of moral purity - but also pursue a variety of political agendas.
When one blogger encounters official disapproval, others rush to his (or her) defence.
This has been the case after Fouad al-Farhan was arrested on 10 December.
The news first appeared on the internet. It took the authorities more than two weeks to acknowledge he was being held.
An energetic campaign is under way online, in English and Arabic, to press for his release.