At some point in the process from raw idea to deployment of a new site design, it will need to be populated with content. Whether it’s a new design or a redesign of an existing site, a designer will need to consider the needs and constraints of the content in order to make intelligent decisions about layout and styling.
So the buck stops here, in your Photoshop compositions, or in your HTML and CSS mockups, if that’s the way you work. You need to use real content.
If I had my way, sample content collection would occur much earlier in the process. The reality is that in many cases, UX documents will contain a lot of placeholder content, or for smaller jobs, design grows out of sketches and essentially starts from scratch.
Lorum Ipsum (or Bacon Ipsum, or Space Ipsum, if it pleases you) is a form of hand-waving. It’s fine for very initial sketches, but the earlier it can be replaced with more representative content, the better.
Practically speaking, real content will help the client-side stakeholders better understand a design. They get a better sense of the messaging and organization of information on the pages, and not just the appearance. In the case of a publishing site, editors can understand constraints on lengths of copy and the different forms of copy needed for each article. Production people can tell you whether they have the ability to generate the type and number of images each layout requires. Lorum Ipsum is a sketch of writing, meaning that both the client and designer project their own assumptions on it, and these assumptions can lead to misunderstandings that can cause headaches down the line.
And because Lorum Ipsum is essentially unreadable (being a dead language and all), it creates a blindness towards the typographic details in a layout. Testing a typographic layout means stepping back from line-heights and type sizes and actually reading the words. Writing styles can vary across different types of media, and so it’s worth pouring some real words into text boxes to test typefaces, sizes, and line-lengths.
For me, a big part of using real content is in creating the illusion of the real site in the static designs. Designing for clients is essentially bespoke tailoring, not an off-the-rack suit. Real content shows that the designer has gone to the trouble of looking at the job in greater depth. It also means more work, because getting sample content from clients can be like pulling teeth, and in the case of a new site, may mean going out and searching the web for like content as a substitute. But the extra few hours spent on the task will help your designs more effective and more convincing, and make the process of client interaction much smoother.