Net-flix has attracted more than 20 million subscribers, more than 20,000 movies and television shows for its online service, and more than its share of headaches in Hollywood.

There's one thing it has yet to attract: competition. Netflix (NFLX) is the only company that streams a large selection of movies and TV shows online for a monthly fee.

That will probably change. Retail giants such as Wal-Mart Stores, Amazon.com, and Best Buy, Internet television provider Hulu, and satellite broadcaster Dish Network are weighing plans to launch online subscription video services or expand nascent ones to take on Netflix, people with knowledge of the matter said.

Such moves would win cheers in Hollywood, where many are worried that Netflix is amassing too much clout. Some also believe that Netflix's fast-growing customer base is buying fewer DVDs and watching less television, contributing to the financial struggles of studios.