By Iain Mackenzie
Newsbeat technology reporter
Bitten by a Zombie? Become a pirate? Take the 80s music quiz?
Some of them may be annoying but Facebook's applications have played a large part in the site's success.
The free plug-ins are created by amateur and professional software developers.
They allow users to customise their personal pages.
Among the most popular are "Causes" which lets members to show their support for a campaign, "Hug me", a way of expressing electronic affection, and "Super Poke" which involves throwing sheep at other people.
Now a change in the way applications are promoted has caused a row.
Facebook is offering to "verify" applications for a $375 (£250) annual fee.
After going through a testing process, successful apps will be given a badge, showing they meet certain standards.
Verified applications will also receive heavier online promotion.
Users' anger
The system will effectively create trusted applications which users could rely on to be virus-free and which protect their personal data.
However, the move has been greeted with scepticism and anger on Facebook's own developers' blog.
Users have left comments including: "Is this a joke?"
One member, cyMall, posted: "This is only going to take away from new apps wanting to launch.
"I don't know of many new apps that have $375 (£250) to throw away to start up on a platform that has always been free."
Facebook has defended the scheme. Platform program manager, Sandra Liu Huang, said the verification program was designed to "…provide your applications with a way to stand out and reassure users that they will provide a good experience."
Application creators can make money by embedding advertising within their apps.
Approved status will give them increased prominence on the site.
Some developers fear that verification may affect Facebook's popularity.
Hakim Sadik is co-founder of Facebookster, which develops applications for companies that want to exploit the commercial possibilities of social networking.
He said: "If you look, at the time Facebook traffic picked up it was when the API (application development tool) was opened up to developers.
"I think it will increase the quality of applications but traffic will decrease."
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