Tumblr’s ​Marketing benefits and value

Tumblr’s Marketing benefits and value:

How useful is this tool for marketing? Which industries are using it the most? Which companies are using it most effectively? For what purpose (trial, awareness, desire, loyalty etc.)? Show examples of successful/effective use of this tool and examples of company failures using this tool for marketing purposes. Which industries might benefit the most from using this social media tool? Which ones might not find it valuable?