I just finished reading "Assessing Student Progress Using Blog-based Portfolio" by Kathy Cassidy. The article link was listed on ACTFL's email news digest. So I have some faith that the mentioned approach is appropriate for the language classroom as well.
I used portfolio for a few occasions. When I was a graduate student at University of Nebraska-Lincoln and took the language teaching method class, I had to create a portfolio, a physical one with the binder, cover sheets, and artifacts (I put in photos, CDs, and etc.). The process was a bit messy. But the result was actually very beneficial. I continued to add to the physical binder when I started teaching and eventually burned a CD portfolio, which is easy to carry around. I don't know for sure but I think it helped me land my second job. When I taught Spartanburg Day School, an IB (International Baccalaureate) school, we all used portfolio to store and assess students' work. Again the portfolio is a physical folder or a binder. Again, a lot of paper and organization was involved. A fun, and a bit messy process, all in all. However, portfolio is definitely the most telling piece when the teacher, the student, and the parents want to see the progress (considered as the summative assessment). I didn't think the portfolio at that time was more useful than any other paper evidence to indicate any changes the teacher might make for the instruction (considered as formative assessment, assessment of students' learning to inform the teacher how effective is the teaching). The real challenge is to make the physical portfolio. Collecting all the pieces, selecting the keepers, and tossing out the "junk"; it is time consuming. For those who lack focus or organization skills, this process is frustrating.
Although I haven't used blog as the digital portfolio, I can see its potential to replace the binder. First of it, it is easier to browse and organize the content. Usually blog automatically organize all entries chronically. The author can also create tags, which are common themes of these entries, and organize the posts using these tags. To browse, one can either scroll down, or click on specific time or tags. To delete and to add things are just clicks away. Videos, photos, and other media can be easily embedded, edited, and viewed by the author as well as by the audience. Assistance from the adults are still needed, in my opinion. Giving assistance is a way of getting involved. There are many other ways to engage the larger community, for example, share these blogs and invite community members to comment on these blogs. Safety and privacy is an issue. But you might just lose your binder and the whole world can see what's in it (or at least the whole school to see). Losing binders, nowadays, happen more often.