@email@example.com Right. TOFU's also long been used in PGP/GPG, and is arguably more widespread than the Web of Trust.
A widely practices mis-assertion of a key is likely to result in a public disavowal ... eventually.
For someone with a particularly high threat function / risk calculus, that's not attractive. And for most casuals, it's yet another idea that can lead to bad practices / poor decisions which might later be regretted.
@firstname.lastname@example.org TOFU's prevalence shows though that even with strong crypto and good tools, validation mechanisms are largely informal.
Recently, the handling of online defamation has become a hot topic on many mass media as well as social media channels. News Article for Reference: https://www.jiji.com/sp/article?k=2020052500387 In response to these reports, it is expected that lawsuits and disclosure requests will become more publicly known; and government agencies will order stricter enforcement in addition to tightening regulations. However, under the current state of Japan, we will not be able to handle the increase of such administrative burdens and will have trouble dealing with it appropriately. Thus, we have decided to stop providing our service on mstdn.jp and mastodon.cloud starting June 30, 2020. We are very sorry for the inconvenience and appreciate your understanding on the matter.