Some users of MySpace feel as if their space is being invaded.

MySpace, the Web’s largest social network, has gradually been imposing limits on the software tools that users can embed in their pages, like music and video players that also deliver advertising or enable transactions.

At stake is the ability of MySpace, which is owned by the News Corporation, to ensure that it alone can commercially capitalize on its 90 million visitors each month.

But to some formerly enthusiastic MySpace users, the new restrictions hamper their abilities to design their pages and promote new projects.

“The reason why I am so bummed out about MySpace now is because recently they have been cutting down our freedom and taking away our rights slowly,” wrote Tila Tequila, a singer who is one of MySpace’s most popular and visible users, in a blog posting over the weekend. “MySpace will now only allow you to use ‘MySpace’ things.”

Ms. Tequila, born Tila Nguyen, has attracted attention by linking to more than 1.7 million friends on her MySpace page. To promote her first album, she recently added to her MySpace page a new music player and music store, called the Hoooka, created by Indie911, a Los Angeles-based start-up company.

Users listened to her music and played the accompanying videos 20,000 times over the weekend. But the Hoooka disappeared on Sunday after a MySpace founder, Tom Anderson, personally contacted Ms. Tequila to object, according to someone with direct knowledge of the dispute. She then vented her thoughts on her personal blog.

MySpace says that it will block these pieces of third-party software — also called widgets — when they lend themselves to violations of its terms of service, like the spread of pornography or copyrighted material. But it also objects to widgets that enable users to sell items or advertise without authorization, or without entering into a direct partnership with the company.

A MySpace spokeswoman said yesterday that the service did not remove anything from Ms. Tequila’s page. “A MySpace representative contacted her and told her that she had violated our terms of service in regards to commercial activity,” the spokeswoman said. “She removed the material herself, after realizing it was not appropriate for MySpace.”

Ms. Tequila and her representatives would not comment.

But Justin Goldberg, chief executive of Indie911, said MySpace’s actions undercut the notion that the social networks’ users have complete creative freedom. “We find it incredibly ironic and frustrating that a company that has built its assets on the back of its users is turning around and telling people they can’t do anything that violates terms of service,” he said.

“Why shouldn’t they call it FoxSpace? Or RupertSpace?” Mr. Goldberg said, referring to the News Corporation’s chief, Rupert Murdoch.

The tussle between MySpace and Indie911 underscores tensions between established Internet companies and the latest generation of Web start-ups. Without a critical mass of visitors to their sites, many of these smaller companies are devising strategies that involve clamping on to sites like MySpace and Facebook and trying to make money off their traffic.

MySpace, meanwhile, is trying to show that it can generate stable revenue. Google will pay it at least $900 million over the next three years to serve ads to the site’s users. And last fall, MySpace announced a partnership with Snocap, a San Francisco-based company, to sell music.

Perhaps not coincidentally, this year, MySpace blocked widgets from Revver, a video-sharing site that embeds advertisements in its clips, and Imeem, a music buying service.

“Our users weren’t happy,” said Dalton Caldwell, Imeem’s chief executive, who was nevertheless ambivalent about the MySpace ban because he thought the move might encourage his users to visit his site directly. “If MySpace isn’t really ‘their space’ after all, maybe users will think about things differently.”

In the past, MySpace executives have said that the service failed to block companies like YouTube that began successful businesses from MySpace’s pages.

“We probably should have stopped YouTube,” Michael Barrett, chief revenue officer for Fox Interactive Media, a part of the News Corporation, said in an interview in late February. “YouTube wouldn’t exist if it wasn’t for MySpace. We’ve created companies on our back.”

MySpace and its corporate parent say they want to find ways to support and exploit the growing widget economy. Last year, Fox Interactive Media introduced a service called Spring Widget. The service provides tools to help developers create widgets for use both on computer desktops and online networks like MySpace.

In a recent use of its technology, the studio behind the horror film “Dead Silence” used a Spring Widget tool on its promotional MySpace page to count down the minutes until the film’s release.

Fred Wilson, a New York-based venture capitalist who invests in social media companies, said the strategy showed that the News Corporation was trying to take advantage of growing interest in widgets while also trying to carefully control what made it onto MySpace.

But that could be a dangerous strategy, Mr. Wilson said.

“Every attempt everyone has ever made to try to dictate what a person’s Internet experience will be has ended up coming up empty,” he said. “You have to accept the fact that you are never going to be the be-all and end-all of everyone’s experience. They are one click away from everyone else on the Web.”

As for Ms. Tequila, who wrote on her blog that she was a personal friend of Mr. Anderson, the MySpace co-founder, she wrote that she felt bad about blasting the site but that she could not stay silent.

“You guys used to be so cool,” she wrote of MySpace. “Don’t turn into a corporate evil monster.”

Louise Story contributed reporting.