The process of getting a .bib file from Paperpile to writeLaTeX is currently a bit long-winded. It'd be great if automatic import could be added... though I expect this might require some work on Paperpile's end.
Great idea! I think you’re right that this would require some help from them to expose the appropriate API. I see you’ve added a comment to their forum, which is a great start: http://forum.paperpile.com/t/latex-paperpile/61 Thanks!
Nils Loewen commented
I sank 8 hours into curating a bibtex library with some disallowed letters or symbol. After that, I abandoned Overleaf and went back go GDocs and Paperpile.
If Paperpile were somehow integrated I'd give it another shot because it is nice to have all formatting according to Journal guidelines (e.g. those miniscule requirements that copy editors always find like hard returns in tables or figure abbreviations - that is baked into a Latex template).
Apparently, Latex is terribly ineffective compared to even MSWord (which I don't use anymore): Knauff M, Nejasmic J. An efficiency comparison of document preparation systems used in academic research and development. PLoS One. 2014;9(12):e115069.