Someone asked me: “If Lightroom doesn't use the embedded jpegs, why bother create them at all?” If you don't use other apps to examine your DNGs, I don't see much reason at all right now.

In fact the other day I saw a rather silly and unsubstantiated blog post (not worth linking) that alleged LR's release was a nail in DNG's coffin. The reasoning was loose - non destructive editor equals abandonment of DNG - but the conclusion was something I thought could be reasonably argued from LR not exploiting DNG. I suspect that's more due to Adobe's priority being to get the program released, and waiting for a new DNG specification to be agreed.

So I am continuing to build large previews because I hope Adobe will make use of the larger previews before too long (and because I still use iView). There are also longer term archival issues such as having a rendered preview of the data, which other applications would be able to read.