This may be an indication of my short-attention span, but placeholder text used as the label has been bugging me for a while, and it seems to be getting more popular. I use it on the web version of this blog; the Search function in the top right uses a placeholder, though if you’re using Internet Explorer you won’t see anything unless it’s IE10. And if you’re using Firefox then older versions will result in the text clearing on focus, unlike Chrome (and presumably other WebKit browsers) where it only clears on user input.
HTML in a consistent manner and that there’s some placeholder text identifying the input that’s been designed to disappear on the text box receiving focus. Or imagine I’d used jQuery. For a single input field it’s a fair solution but for more than one it doesn’t work; I’ve found it niggling for something as simple as the usual three prompts (email, name and website) before adding a comment.
Proponents will point out the snapshot is unfair. In real life I’d be entering this information together; I’d know what I’d just clicked on. This might be true for some, it depends on the point at which your focus moves to the next field; is it before or after you click? For me it’s ‘after’, or would be if I used the mouse (or similar) to navigate the input. However, I use the keyboard and, I suspect like most who do, my focus doesn’t move until I tab away; hence my attention would only move to the next input field after it had already received focus, and lost its identifying label. Therefore if there is placeholder text it shouldn't clear until the input has content, though I'd question whether user content is an adequate identifier.