Stack Overflow, a popular Q&A service for programmers, has been acquired by European investment firm Prosus, co-founder Joel Spolsky announced Wednesday, for a price tag of $1.8 billion, per the Wall Street Journal.Why it matters: Stack Overflow's success at enabling expert developers to share tips and shards of working code became the foundation for many novices' knowledge and built a community that helped more advanced practitioners solve tough problems.Get market news worthy of your time with