Following on from a theme that Simon has been pursuing here is an interesting piece - How SimpleDB differs from a RDBMS. A thorough analysis of SimpleDB, but I think the extra value here is in the comments. I particularly liked Greg Jorgensen's submission that programmers just don't like RDBMS because they take some learning. Whilst I don't have empirical evidence to back up this supposition I can say that most Java programmers I've come across go slightly green if you suggest that they can solve most problems with a SQL statement (and yes, that was meant to be read ironically).
If I can sum up the message of this post and it's comments it is that we should be thankful for having different tools available to us, because this isn't a one size fits all world. Where you've got a big list of simple things (tm) tools like BigTable and SimpleDB work well. Where you've got large pieces of unstructured data (sometimes referred to as 'documents') you can use CouchDB, and where you have complex, structured data that has to adhere to certain validation and usage rules use a relational database. Each of these will store up to terabytes of information so let's not even talk about (the myth of) scalability. Choose the right tool for the job and stop insisting that every problem is a nail.
So to answer my question from the title of this post - still around, and still kicking arse.