I know its been mentioned before, but what are Pownce's largest competitors at this point?

Pownce seems to have incorporated the usefullness of 37 signals into their framework as a business app tool, but with the stream it is more similar to micro blogging sites such as: tumblr, jaiku & twitter. Would it be safe to say Pownce is a microblogging site as well as a file sharing app?