There are many good reasons for choosing open source over proprietary software, notably the freedom it gives you, and the security that comes from allowing anyone to look for bugs.
Here's an amazing example of what by contrast can happen with closed source in this regard:
Microsoft took the unusual step today and skipped patching one of the vulnerabilities addressed in its monthly security update, saying that crafting a fix was "infeasible."
The omission leaves users running Windows 2000 Server Service Pack 4 (SP4) vulnerable to attack.
This is extraordinary: it means that Windows 2000 becomes abandonware – no longer fully supported by its manufacturer, and left with a critical security flaw that makes it pretty much unusable in many circumstances.