The professors, lawyers and writers detained last week in several Saudi cities had been critical in newspaper articles and TV appearances of the kingdom's strict religious environment and the low pace of introducing reform.
Arresting them was seen as a message to more influential Saudis that the government is not softening on dissenters of any stripe.
Najib al-Khunaizi, a detainee freed this week, said on Sunday that the men had to make a written pledge not to sign petitions calling for reform or talk to the media.
He insisted on Saudis' right to "freely express themselves" and said he had been treated well, but had signed the pledge under duress.
Some of the reformists signed a letter addressed to Crown Prince Abd Allah at the end of last month calling for a speedy introduction of political, economic and social reform, including elections of the Consultative Council, which acts as a parliament and is appointed by the king.
Others demanded the absolute monarchy should be changed into a constitutional monarchy and that Saudi Arabia review its relations with the United States.
"Those guys who were detained and the ideas they represent have made a lot of waves, sparking a lot of debate"
Ibrahim al-Mugaitib, head of Human Rights First
Some criticised the new National Human Rights Association whose members are appointed by the king, and declared their right to establish an independent rights group.
"Those guys who were detained and the ideas they represent have made a lot of waves, sparking a lot of debate," said Ibrahim al-Mugaitib, head of Human Rights First, which is active despite government refusal to respond to a request to license it more than a year ago.
Al-Mugaitib said seven of the detainees were released.
"The government was afraid the debate would not remain a debate in the papers," he added.
The government has accused the men of incitement and of using the names of prominent Saudis in petitions without asking those people's permission first.
US State Department spokesman Adam Ereli condemned the detentions last week as "inconsistent with the kind of forward progress that reform-minded people are looking for."
Angered by what it saw as US interference in an internal matter, the Saudi Foreign Ministry responded by issuing a statement saying it was "disappointed" by the US reaction to the arrests.
Saudi reforms are occurring at
too slow a pace say critics
US Secretary of State Colin Powell expressed concern over the detentions during a meeting with Crown Prince Abd Allah in Riyadh on Friday.
Despite their activities, the men do not carry the kind of importance, political weight or popular base that would have undermined the government.
The Saudi government began a cautious move towards reform following the 11 September 2001 attacks, carried out by 19 hijackers, 15 of them Saudi.
It has encouraged debate and allowed newspapers more freedom to criticise.