The answer is, maybe.
If you are unpublished -- maybe.
If you are a picture book writer -- maybe.
What about developing platform? That's mostly for nonfiction writers.
Along with the information we gave at the MD/DE/WV SCBWI conference recently, here's more blogging info from agent Mary Kole, at Kidlit.com who is holding a conversation about this very thing.
There are many good ideas in the comments, pro and con.