Vendor lock in. I will not touch any IM services that is not completly open (client and server) and federated. I am looking for matrix.org that uses Olm [1] for E2E encryption.

[1] https://matrix.org/git/olm

VC backed (Iconical, Skype co-founder Janus Friis who's involved in product dev), premium features + platform play targeting enterprise will monetize.