Actually posing in Maxim was probably a good career move for Hart. She’s been lucky and had two hit series, but at 23 she has to break out of her public image as a cute teenager if she hopes to have an ongoing career. Otherwise she’s heading for Molly Ringwald territory.
IIRC, a couple of years ago some magazine did an article about the 7 “sexiest” females of TV at the time. There was an accompanying photo spread with the 7 women posing as if at a pre-teen slumber party. Among them were MJH (pre-Sabrina), Jeri Ryan (ST:Voyager), and [I think] Alyssa Milano (Melrose Place).
The photos there were just as provocative as the Maxim spread.
Oops. It was Jamie Luner, not Alyssa Milano. And the mag was Details.
Here’s Jamie, Melissa, and Jeri striking a pose. 
So, to make my point (before I hit “Submit”): MJH has already done a provocative photo shoot while she was playing Sabrina. What the big deal?
Do the he networks really expect the actors/actresses to emulate the characters they portray?
MJH is attractive, rich, and smart. Do they really expect her to stay at home on weekends? To go on wholesome family vacations? No way! She heads to Cancun, just like any other 20-something with the means would do!