People are particularly emotional about Coinbase because it touches on their bottom line -- money. But let's not forget the fact that ALL startups have major scaling woes. Bugs in the tech being ironed out, overwhelmed support and engineering teams recruiting and integrating talent to meet the demand -- in Coinbase's case exponentially growing demand. If you've worked in a software startup you know how easy it is to be met with exponential increase in demand, and how impossibly difficult it is to stay above water growing a team at the same rate.
I'm positive on Coinbase due to their backing. YC, Andreessen Horowitz, DFJ, among dozens of high-profile investors. These guys want a $20B valuation, they're not interested in backing a failing company or a scam.