As far as the application is concerned, it can be used for perhaps for a optical company branding? The recognition factor is a huge asset in branding.
Legibility argument falls apart - otherwise we wouldn't have Zapfino and Bodoni. In certain situations, legibility takes a backseat over stylistic intentions. In other cases, yes you're right - I wouldn't want my blood test results to be misread. Another area where fonts can have devastating effects is say for example lack of a slashed 0 in nuclear missile launch codes. But we are in good hands with respect to typography and design for serious things - the Martin Baker EJECT seat handles in fighter jets don't use comic sans and they have bright yellow stripes for super fast visual recognition. :-)