You say this like Twitter is supposed to be the bastion of web security or something. Twitter has always been a poster child of web security vulnerabilities and scalability issues.
Why can't Twitter get its shit together? When Facebook faces those kind of problems, they iron them out in a blink of an eye. Scaling problems? No problem, I don't think I've ever experienced Facebook going down in the past 4-5 years!
How can a top-10 Alexa site such as Twitter continually entertain users with hours of downtime every week? What about escaping input? This is below web dev 101 for god's sake.
The books category is especially ridiculous. You might have read some books in each one of those levels, and they're not exactly prerequisites to one another.
I also use Git exclusively, that doesn't mean I'm proficient with SVN.
You're thinking like a movie critic more than a business owner. The quality of the reviews counts for squat if the cash flows are positive. In the end, Google thinks it's a financially sound acquisition aligned with the company's vision. That is what matters.