From RPGNOW’s website:
Wizards of the Coast has instructed us to suspend all sales and downloads of Wizards of the Coast titles. Unfortunately, this includes offering download access to previously purchased Wizards of the Coast titles. We are in discussions with Wizards about their decision to change their approach to digital sales of their titles and will post more information as we have it. If you would like to let Wizards know your opinion on offering D&D titles for download, we suggest the D&D Message Boards found here.
It seems piracy has become an issue, as stated by WOTC_Trevor on the ENWorld boards:
Unfortunately, the truth is that due to recent findings of illegal copying and online distribution (piracy) of our products, Wizards of the Coast has decided to cease the sales of online PDFs. We are exploring other options for digitial distribution of our content and as soon as we have any more information I’ll get it to you.
Let’s see where this leads, although I’d be majorly pissed if I paid for a book that I couldn’t download now… This may be counter-productive folks, let cool heads prevail here…
www. Newbie DM .com 
Wyatt
April 6, 2009
It’s a dumb move. Yeah, Wizard’s, because nobody has SCANNERS. Magical artifacts which, as an at-will power, can copy the pages right out of your books and send them to the internutz from which you can never retrieve them.
If anything sucks the life out of 4e it might be this one. And I love 4e, but damn.
Zachary
April 6, 2009
Agree with Wyatt. I mean, hell, I bought a lot of 1e and 2e stuff from WotC. Now they’ve effectively severed the last interaction I have with them.
People can get this stuff from a torrent in a half-hour. The people who wanted to pay for it, now can’t. And when/if they do put PDFs back for sale online, where’s the confidence they won’t do it again?
Poorly done, WotC. You continue to fail your PR roll.
Sal M
April 6, 2009
I’m betting dollars to donuts that this is because a leak for PHB2 came out that was sourced to an online retailer. The printers were the source at launch, so now it’s Online’s turn for the whackamole targeting reticule.
Wyatt
April 6, 2009
My consolation is that after seeing PHB2 offer me absolutely nothing of value over PHB1, I won’t really be buying those anymore. After Arcane and Divine Power (I’m not going near Primal Power) my collection will pretty much be complete.
Zachary
April 6, 2009
That’s cool you have a possible “I’m good” point, Wyatt. I didn’t do that when I played Rifts and ended up with 26 Worldbooks. 🙂
Daniel M. Perez, The Gamer Traveler
April 7, 2009
/sigh
Don’t they listen to my show, The Digital Front? Don’t they simply know that it is just bad for their business?
I’m not entirely surprised, though. WotC doesn’t have the best record when it comes to the digital publishing field.
I hope they reconsider.