Worked in 10 startups as a contractor, got to see some interesting trends, and also compared with fellow developers in other startups. We found that one or more of the following indicators would reek strongly of a startup that has a big technical risk (e.g. poor architecture choice, obscure platform and language decisions, etc.)
1. CTO or lead developer has worked for Google.
2. CTO or lead developer decides to use AWS as they "feel" it is right to do so.
3. CTO or lead developer decides to use Python, but wants to write in EE Java. Some the code becomes contaminated by statics, getters and setters, and verbose POJO style approaches, and very unpythonic code.
4. CTO or lead developer decides to criticise or rewrite good Pythonic code from experienced Python developers into the in-house Java EE style.