At the end of The Last Name, Soichiro Yagami says that Misa has once again lost her memories of the Notes, to which L responds that it is probably because both Notes have been burned. If that's the case, how do L or Yagami remember anything about the notes? Did burning them also wipe out related memories of everyone in the task force who had touched the Death Notes? What about any written material they might have created before burning the Notes?
I haven't watched the anime or read the manga.
A lot of this is answered indirectly in the manga/anime. I'm spoiler-blocking much of this because I don't remember how different it was from the live-action movie.
The memory loss is very targeted, leaving related memories fuzzy. For example, there's a point that shows this pretty clearly:
When Misa gives up ownership, she still remembers Light, and is in love with him. She remembers going to Aoyama, as well as that being where she first saw and fell in love with him. She doesn't remember why she went there (to find Kira), nor what she was wearing (a disguise so she couldn't be identified later as having met someone at the same time Kira and the second Kira met).
Their identity as "Kira" is completely tied to the Death Note and would not exist without it, so both Misa and Light forgot that they were Kira when they gave up ownership.
The anime also goes into letting another use the Death Note while retaining ownership, and things like that. For example, again in the anime:
When Misa first met Light, she gives him her Death Note for safekeeping, but doesn't give up ownership. She keeps all her memories as well as the eyes.
Later, when Misa gave up ownership of her Death Note, Light could still see Rem; he was unaffected. However, Misa could no longer see Ryuk, so the memory loss affected more than just what came of her Death Note.
I don't recall the live-action movies well enough to say for sure, but if I can assume that the people you're asking about didn't have ownership:
