Reboot

Back in 1984, DC took what was a radical step: Rebooting massive chunks of its continuity in the wake of the Crisis on Infinite Earths series. No more parallel Earths and multiple futures. Superman had never been Superboy and Supergirl never existed. Wonder Woman was just starting her career years after the other heroes.
Unfortunately, a step DC intended to simplify everything confusing about continuity (whether or not it was that confused is another question) soon got confused instead. Several individual characters, such as Hawkman, got “crisised out” and rebooted (including adventures that had happened after Crisis, when the timeline was supposedly stabilized). Even some creators began complaining it was hard to know what stories were canon.
So DC tried stabilizing continuity in the Zero Hour series, but the reboots kept coming. And then it rebooted a lot of reboots in Infinite Crisis (Wonder Woman started when everyone else did).
And now they’ve announced a new rebooted universe spinning off the Flashpoint miniseries. Like Crisis, some heroes go through unchanged, others start over (Wonder Girl is a thief, Tim Drake is no longer Batman’s ward) and others get thrown back (Barbara Gordon, who went from being Batgirl to computer-hacker Oracle after she was crippled is now Batgirl again).
Words cannot begin to express how much this annoys me——and I don’t even read that many current books.
The theory is that quite aside from the initial PR boost (which seems to be working), starting over fresh on a lot of books will attract new readers. And the heroes will be conspicuously younger in many cases, in the assumption that this will also draw teen readers (teenage comic geeks have never had trouble with an adult Batman, Flash, Green Lantern, Iron Man, Superman etc. but it seems to be an axiom that young heroes are the only way to go).
The downside of that, as others have pointed out, is that it can kill the attachment people have to the character they grew up with. The new versions of Red Robin, Kid Flash and Wonder Girl clearly have no relation to the originals, which makes it much harder to feel invested in them (at least it did for me with many of their past reboots).
Of course, comics have always had continuity errors, glitches and origin revisions, but prior to crisis they made some attempt to acknowledge a consistent continuity. But if anything can be overturned and changed at any time, it makes the illusion of any sort of reality unsustainable.
And a great deal of the changes DC has worked in the current century seem, if anything, more about appealing to fortysomething comics writers. If you started reading comics sixteen years ago, Wally West was the Flash, Connor Hawke was Green Arrow and Kyle Rainer was Green Lantern; bringing back the Silver Age versions must have gone over for some younger fans about as well as if the post-Crisis reboot had replaced everyone with the 1940s versions of the character (“There never was a Barry Allen——the definitive Flash was always Jay Garrick!”). I imagine some will feel the same about Oracle now being Batgirl (quite aside from the fact there’s lots of Caped Crusaders and only one Oracle.) I discuss this more here.
Ditto the (anticipated) erasure of the Clark Kent/Lois Lane marriage: There’s nothing that makes the Silver Age Clark/Lois/Supes triangle “definitive” (as new Superman-writer Grant Morrison has claimed) other than Morrison growing up with reading it (heck, even Jerry Siegel didn’t think it was definitive——he wrote a never-published story in which Lois learns Superman’s secret identity and becomes his sidekick/partner).
I was going to say something else, but wedding planning calls. So later!