As the tools for source code control evolved, one particular one emerged and became dominant for a long time. It is even still widely used today. It is Micro$oft's Visual SourceSafe (VSS). Here is why that is a very bad thing, why your project shouldn't do it and what to do if that mistake has already been made.

VSS

Reasons to avoid VSS:
  • It is only available for Micro$oft platforms.
  • It lacks usable branching support.
  • It silently leaves stale files on your local system.
  • It degrades on large projects. Micro$oft recommends that your database not exceed 5 GB.
  • There is high risk of corruption: Micro$oft recommends that you run the Analyze diagnostic program weekly.
  • Micro$oft do not each their own dog food. They use a modified form of Perforce. It's not hard to figure out why.
  • It's expensive. It is a separately purchasable product.
  • It's expensive. You have to pay per VSS client! See this MSDN forum thread
See the links below. It's not just me that is against VSS.

Links