Just a small accessibility thing: having inputs with placeholder text is great, but screenreaders have not caught up with the times and you should still use a corresponding <label> tag.
Agreed. If people insist on "styling" with placeholders as labels, they should at least include <labels> that are hidden visually but accessible by screenreaders.
It also results in ugly rendering issues with browsers that save previously submitted form data, overlaying it on top of the placeholder text or replacing it even if it's the wrong data for that field type.
The issue is that the placeholder text disappears once you start typing into it. The usability assumption is that once you start typing in a value you no longer need the placeholder, but that is a bad assumption, particularly if a mistake is made as the gp is alluding to.
Also, just as a general user experience thing, not having labels can be detrimental if the field's purpose is forgotten or unknown. Having a placeholder is fine if there is no value in the field, but if I submit a long form after filling it out, only to be shown an error, what if I don't remember what that particular field was for?
Has anyone done any studies on what % of web users use/need screensreaders? Supporting such technologies can be quite cumbersome. Also, is screenreader support mandated or addressed under the Americans With Disabilities Act?