The threat to the hugely popular Scrabulous game has galvanised Facebook members into mounting a vigorous defence campaign.
The Save Scrabulous group is growing quickly on Facebook
In little more than a day more than 13,000 people have signed up to a Save Scrabulous group on Facebook.
Many have signed a petition asking Mattel and Hasbro to back down from their threat to have the game removed.
Others have bombarded the two toy makers with letters, e-mails and calls asking them to preserve the game.
The joint owners of Scrabble, Mattel and Hasbro, launched their action on Tuesday saying that the Scrabulous game was a "gross copyright and trademark infringement". The companies asked Facebook to remove Scrabulous.
Neither Facebook nor the Indian brothers who created the online word game have so far commented on the row.
On Facebook, Scrabulous regularly racks up more than 500,000 users a day and many of these have leapt to the defence of the game.
A Save Scrabulous group has been created on Facebook and in little more than a day more has more than 13,400 members.
Discussion on the group has been broadly critical of Hasbro and Mattel and many have called on the toy makers to "back off" and leave Scrabulous running. In comments many Save Scrabulous members said they would boycott Hasbro and Mattel products if the game disappeared.
HAVE YOUR SAY
If Mattel and Hasbro have any sense, they'll work with the creators of Scrabulous
Ben, Sheffield, UK
Some said the decision to launch the legal action was "short-sighted" and could only damage their reputation. In one discussion thread more than 100 people said playing Scrabulous had led them to buy a copy of the board game.
"Never played Scrabble until I played 'Scrabulous'," wrote Alexandra York. "This is the best application on Facebook and has brought Scrabble to many people who have never played before whilst allowing friends and family to enjoy the game in spite of living far from each other."
Jeff Wismer from Toronto wrote: "I completely agree however that their trademark has been hijacked and it's within their right to take action. They just have to make sure that action isn't shooting themselves in the foot."
Contact details for executives, customer service and complaint departments at the toy makers have been posted to discussion groups on Save Scrabulous.
Many members of the group posted information about the responses they were getting that the companies are being bombarded by concerned fans of the game.