IANAL, but if 4epowercards.com was my site, I would've been tempted to see what the courts would've said about the matter.
Selling someone else's work as your own is wrong, but thats not the case here. No money changed hands, and no credit was taken--the text in question was obviously quoted from the PHB and other WotC books.
Also, as stated above, the powers themselves are incomplete information, so you couldn't possibly reverse engineer the game rules from the power cards. The powers use terms which are only defined in the core books, so you could know that a power came into affect when a creature was 'bloodied', but you wouldn't know what 'bloodied' meant unless you used the rule book itself. And why would anyone even want the cards unless he or she was already playing the game, (i.e. is also a WotC customer)?
To me, this is a case of someone simply providing a service to aid the playing of a game. Take chess for example--if someone made free cards for each piece that described how the piece moved, even if quoting from rules printed by another company, what's the problem? To play the game, you would still need a board and pieces. The cards only assist with playing, they don't eradicate the need to purchase the game.
And assuming that both sites that were recently shut down were violating WotC's copyright, my question is this: why didn't either site merely change their content enough to comply with the law?
In the case of 4epowercards.com, replacing the actual text with a paraphrased version is all that would've been needed, (and the removal of any D&D or WotC logos or trademarks, if there were in any in use).
But in both cases, the sites were shut down with ONE very brief comment from the creator, which means that the creators both signed non-disclosure agreements, AND one of two things:
WotC used such heavy handed tactics that the site creator was scared into going away and signing the NDA, OR WotC was really nice about it, and paid the site creator a significant amount to go away and sign the NDA.
You can see how, in both cases, it behooves WotC to keep the details of the deal quiet, and I would love to know how both went down.