They fall in two directions: Suspected Iranian plots and fears about Islamists emboldened by Arab Spring victories in Egypt and elsewhere.
Authorities in Bahrain - facing nonstop clashes and unrest since February 2011 - have increasingly blamed Shiite power Iran or its proxies for encouraging the protests by the island nation's Shiite majority. No clear evidence has emerged to back up the claims - and Iran denies any direct role - but it has become a central narrative of the six-nation Gulf Cooperation Council anchored by regional Sunni power Saudi Arabia.
It's also one that boxes Washington and other Western allies into a corner. The U.S. has urged dialogue in Bahrain, where more than 50 people have died in the unrest. But any clear support for the Shiite-led opposition could seriously disrupt relations with Gulf nations and possibly complicate the future of U.S. bases in the region.
In the UAE, the main target is an Islamist group, al-Islah, that authorities worry could try to undermine the control of the ruling clans in Dubai, Abu Dhabi and other emirates. Al-Islah says it only seeks a wider public voice in the country's affairs - but even that is considered dangerous territory in a nation that allows no political parties and swiftly stamps out any signs of public protests.
Dubai's police chief, Lt. Gen. Dahi Khalfan Tamim, warned in September of an "international plot" to overthrow the governments of Gulf Arab countries by Islamist factions inspired by the rise to power of the Muslim Brotherhood in Egypt.
"The Muslim Brotherhood does not believe in the nation state," said the UAE's foreign minister, Sheik Abdullah bin Zayed Al Nahyan, last month. "It does not believe in the sovereignty of the state."
Curiously, the claim came just weeks after the UAE's president, Sheik Khalifa bin Zayed Al Nahyan, offered an invitation to Egyptian President, Mohammed Morsi to visit Abu Dhabi.
The belief in a Muslim Brotherhood threats runs so deep that the Gulf Cooperation Council - Bahrain, Kuwait, Oman, Qatar, Saudi Arabia and the UAE - are expected to make it a main topic of talks when leaders meet next month.
By that time, however, Kuwait will have held its next election for parliament, by far the most politically powerful legislature of the Gulf Arab states. Opposition groups, led by Islamists and backers from Kuwait's powerful tribes, have two main paths ahead: Either seek to reclaim control of the chamber or boycott the voting in protest of the tightening crackdowns.
Hours before a planned protest march on Sunday - in defiance of bans against street rallies - social media sites were awash with appeals to put aside concerns over the tear gas and stun grenades used against the last major demonstration late last month. In an apparent attempt to outwit authorities, organizers switched the location at the last minute from Kuwait City to a suburb.
Some posts cited patriotic songs from a generation ago. "We are the confident steps on the path of hope, like a strong wind that doesn't tire."
Associated Press writer Hussain al-Qatari in Kuwait City contributed to this report.