Just to remind everyone, the only reason I brought up FM in this thread was as a reference point, to compare-and-contrast them with Photobucket's (to my mind unreasonable) bait-and-switch tactic.
In the equivalent thread on the World of Spectrum forums, people agree with me that this is totally unreasonable; not only suddenly demanding a small fortune (and annually to boot) to continue using the account for the purpose (sole purpose in many cases) for which it was opened, but the rude and aggressive way in which they worded it. Posters on the other thread are predicting that this move will prove to be as suicidal as Gerald Ratner's notorious speech in which he denounced the qualiity of his company's products, not realizing that the speech would be reported and that the public would take it seriously.