It appears the nature of the content might be affecting viewability.
For example, Hello-SaiGon.Com is a private label Blog that covers TP HCM. Then there is http://ejRoundTheWorld.blogspot.com which is viewable and has minimal VN coverage.
Another I keep an eye on because of it's content is http://sgeug.blogspot.com (SaiGon Electronic Users Group-Nhóm người dùng điện tử SàiGòn) which is English/Vietnamese bilingual. It has electronics content and is available
My employer is paid to maintain 7 or 8 Blogspot/Wordpress sites and all are product support in English/French/Hispanic. These are all accessible outside VN.
I haven't been able to contact my VNPT commercial technical support this week to get an official take on the situation.