Revisions not enabled but vid NEQ nid

Dah-ha!

Some time ago, I observed on a client project that version id (vid) was not equal to node id (nid) even though Revision/History was not enabled on this instance.  Weirdness.  In the end, it turned out to be something goofy with a mysql crash botched recovery and data restoration at the datacenter, but that's a tale for another time (perhaps over a beer at Dallas Drupal Days 2012?)

So I am trying to create a new "shell of a Drupal instance" for the client with some stub data.  This Drupal 6 based portal was never deployed atop profiles or Drupal Build Tools, so I put on my mud boots, grabbed a shovel, and started wiping out content directly in the db picky-choosey style.  Turns out node_revisions still has to have something in it, but since I wiped it completely, I'll continue with my story.

node_revisions.nid is a normal field, but node_revisions.vid is one of the rare instances where Drupal takes advantage of the native database features like autoincrement: Empty node_revisions and new nodes give old new nid and brand new vid!  See image:

Check your own installations: You'll see that probably nid == vid for most instances.

When can nid != vid be a problem?  When you're starting out and you don't consistently include nid AND vid in your queries in some instances and rely on vid in others....

Because I had cleared out node_revisions, I am seemingly unable to delete some content.  Doh!