Hillary Clinton's basic defense to the entire email scandal has been to play the part of stereotypical aging luddite; it's the one time you see Hillary truly embrace the fact that she is old because it implies that she can't be held accountable for not understanding what grave security errors and violations of the law she committed by setting up her homebrew server.
Recall that her initial explanation was that she didn't want to have to use two devices, ha ha look at the old person who doesn't know you can put two email addresses on the same mobile device. Then remember when she was being grilled about what was left on her server and a reporter asked whether she "wiped" her server, she responded "What, like, with a cloth?"
I think Team Clinton has known from day one that this story was going to be an ugly, slow motion disaster, and so they have decided to make a calculated play on pretending that Hillary's feigned technological ignorance can be used to manage this story forever, both as a means of at least partially exonerating her (from a PR standpoint) and to explain their own shifting story on the scandal.
However, it turns out that Clinton knew full well the security implications of what she was doing, and decided to go ahead and do it anyway. In fact, the Right Scoop has her discussing on tape her knowledge of the security vulnerabilities of blackberries, to which she had become "addicted" during the 2008 campaign:
Furthermore, it seems that the genesis of the entire homebrew server may have been the NSA's explicit refusal to issue her a blackberry because of security concerns:
The NSA actually turned down Hillary’s request in 2009 for a secure Blackberry because they had security problems. But that didn’t stop Hillary from using one anyway, in conjunction with her vulnerable private email server:
CBN NEWS – Newly released emails reveal Hillary Clinton was made aware of security concerns over her Blackberry when she became secretary of state.
She requested a secure Blackberry from the National Security Agency in 2009, but the NSA denied her request.
Officials argued there were security vulnerabilities with using Blackberry devices for secure communications or in secure areas.
Clinton was sworn in as secretary the prior month, and had become “hooked” on reading and answering emails on a BlackBerry she used during the 2008 presidential race.
“We began examining options for (Secretary Clinton) with respect to secure ‘BlackBerry-like’ communications,” wrote Donald R. Reid, the State Department’s assistant director for security infrastructure. “The current state of the art is not too user friendly, has no infrastructure at State, and is very expensive.”
One month after Clinton’s request was denied, she began using a private email account on her Blackberry phone to exchange messages containing sensitive information.
So, when she came to State, Hillary Clinton asked to be issued a "secure" blackberry. She was refused by the NSA because they told her that such a thing did not exist. Hillary Clinton decided that she wanted the blackberry more than she wanted this country's information to be secure. So she set up this (probably illegal) server to meet her personal convenience needs.