A) Availability of required skill set in the local geography to the build the right R&D.
B) High costs of hiring people with desired expertise. Additional costs in benefits administration and in general taking a longer term liability while the business has yet to prove itself.
C) Additional funds requirement to scale up infrastructure to match with the team expansion.
D) Founder management getting swamped with operational issues due to increased team size while they need to focus more on technology, raising funds and new customer acquisition.