Among technical communication teachers, there is a long running debate regarding whether or not students creating web pages need to learn HTML/CSS. Or can they just use WYSIWYG's?
I just finished attending the O'Reilly Tools for Change conference this past week. Whether or not students need to understand HTML for building web pages aside, it's definitely now important for technical writers interested in working in the book publishing industry. The sense at the O'Reilly conference is that ebooks are about to become the dominant publication format over print: Bold Predictions: Half of US Publishers Expect E-books to Be Dominant Format by 2014
Maybe it won't happen in 2014, but it certainly does seem to be coming in the next 5 to 10 years. At the conference, Qualcomm representatives predicted 200 million tablet and ereader devices by the end of 2013. Tablets flooded CES 2010 (see a few of them). People are reading books not only on their iPads and ereaders, but their phones as well.