When I joined Tumblr: March 2009
# of followers: 80,000+
How I believe Tumblr has helped my career: It has definitely been an excellent way to promote my photos, thanks to the reblog feature mainly. Thanks to reblogging and how easy it is to customize your theme and post new material, it is an excellent way keep a blog of your work.
My advice for artists on Tumblr: Post only original content; it is more attractive for your followers, and you will be showing images that are not somewhere else. You can open another Tumblr for liked images or different kind of curated posts. Find a balance between uploading constantly but also not too much.