This recent article is situated in the tertiary sector but still makes a great read. 

Web 2.0 technology, such as blogging, allows for locally developed, cost effective, and holistic alternative portfolio assessment systems. By enhancing critical reflection and fostering social interaction, blogging portfolios are seen as an integral learning tool for all students enrolled in a university program.

Read the full article here: 

http://sloanconsortium.org/effective_practices/bportfolios-blogging-reflective-practice

Or take the easy route and read a couple of perspective that have been blogged by others:

http://etcjournal.com/2011/10/22/at-last-–-recognition-of-blog-based-portfolios/

http://www.dontwasteyourtime.co.uk/eportfolio/eportfolios-are-out-bportfolios-are-in-apparently-eportfolio-bportfolio/