This interesting question has been posed in an online discussion group. Experienced short fiction writers will wince, but others who spend their lives immersed in new media may struggle with the idea that there is any difference. This was my reply to the question. Any comments?
I've been writing short stories for many years, blogging for a few of those and I think the two can go together very well, provided the short fiction is just that, short! 4000 words is ok for a short story, but too long for a blog entry, few will want to read anything that big. 1000 words is flash fiction (though personally I think that's too long for flash, but that's a different discussion!) and is fine for a blog, though even shorter is better.
The other thing is, a short story is a work of art and not written in five minutes. It should be carefully crafted, well edited and exude perfection! Flash fiction should be especially well tended. On the other hand, a typical blog entry is informative, conversational and less formal, not precisely put together; anything goes provided the typos are kept under control. So decide if your blog entry is a work of art or an informative article, and proceed accordingly.
btw, a great place to try out your short fiction is: http://jottify.com/