Is their a such thing as a value tech stock?

First, I should start by stating: am and always have been a value investor. With this principle in mind I am bullish on Microsoft and big pharma. However I am starting to question the theroy of value teck stocks because of a few violators. i.e. Yahoo, eBay, Dell et cetera. These among others were supposedly good values for some time now, only to drop much more. Is this simply a case of poorly managed companies in slowing industries withco increasing competition? Are they just a small exception, or do they just need to mature? What do you think?