Resistance to Facebook's proposed takeover of photo-sharing service Instagram has prompted the UK's main competition authority to announce an investigation into the deal.
And reports suggest that even the possibility of the $1billion (GBP640million) merger being put under the microscope could even put the deal itself in doubt.
The Office of Fair Trading (OFT) is believed to want assurances that the deal won't stop users from uploading their pictures to other social media sites, such as Twitter.
It has asked for views on the plan by July 15, after which the OFT will have to decide whether it has the authority to rule on the deal. This may be in doubt because, although Facebook has a UK office, it is not a British-owned company.
Views could be sought from developers of other photo-sharing apps, as well as other social networks, according to technology website ZDNet.com.
It follows a similar announcement by regulatory authorities in the US. Its Federal Trade Commission has asked Facebook to provide details of the deal to help it decide whether it considers that it meets competition rules.