This year we are using Posterous to share student work with parents. Each teacher has a Posterous site and within that site each student has a private Space. Spaces are accessible only to the teacher and parents. Students post their work from iPads using a general school email account established for this purpose.
We started posting work 2 weeks ago and so far it has gone well, with only a few glitches. There have been 3 problems. First, impatience. Generally work is posted quickly but sometimes it takes more time. Second, incorrectly entering email addresses, or not setting the school email account as a contributor. Finally, on some iPads the school email was "kicked off" the iPad so no email was being sent at all. Luckily once discovered all the problems were easily corrected.
So far using Posterous to create aprivate e-portfolio for students is going well.