I know that this is a comment that could be made about other characters in the James Bond film series (Felix Leiter, Chief of Staff etc.), but here goes on Blofeld:
We know from the original Bond novels that Blofeld is a master of disguise - this being so, he changes his appearance through plastic surgery and weight-loss/facial hair, contact lenses etc. Why then do so many differemnt type of actors portray him on the screen - why not just have the same actor from YOLT to DAF (which in itself, was filmed out of continuity). All three Blofelds look different/behave differently. Why could Charles Gray not just have played a character called Jack Spang or Sigmund Stromberg - he had grey hair like the Blofeld of OHMSS, but he was a very poor Blofeld. Telly Savalas was bald like Donald Pleasance, and he had the requisite "missing earlobes" but he was the only one to reflect some of the characterisation of the Blofeld of the books. Blofeld could have been such a better villain in the film series, as it is he's a pantomine villain from a cartoon strip - a Dr Evil influence in Pleasance form or a fey, theatrical and campy Blofeld as played by Gray in DAF - plastic surgery perhaps explains this face change (Gray also dresses in drag), plus his fate is left unclear. In FYEO we had Blofeld (with neck-brace from OHMSS incarnation) completely blanking DAF as it in turn completely blanks DAF and Blofeld here acts as the punch line to a rather long and silly visual joke in the pre-titles sequence that seems at odds with the revert to serious Bond that summed up the whole FYEO film experience.
I intend to look at the filmic Blofeld in an article called 'The Many Faces and Deaths of Ernst Stavro Blofeld (1964-1981)'.
I do think that with Kananga there was a deliberate attempt to move away from all of the Blofeld/SPECTRE crap of the Dr. No-DAF years and to create a freelance villain that was interesting in his own light and that didn't have to rely on the SPECTRE claptrap as his organisation - he had much more to do as an actor as a result - a great gift that was partly squandered due to Tom Mankiewicz's script.
Thanks for reading. I'd love to hear your views on this vexed subject of Blofeld in the films.