Bitcoin is a very secure and stable crypto-currency; no wonder it's been dubbed “Virtual Gold”. But when it comes to everyday transactions, it's too slow and expensive, and can only process around 10 transactions per second. Many other forms of coin offer better transaction speed and more transactions per second, but so far, none could replace PayPal or credit card companies. At least, not until Nano (formerly RaiBlocks).
I don't think that it is common, but it is something that I had to do: I run a Neverwinter Nights server and because it is quite large, the memory usage of the process was climbing by around 100 megabytes every hour. It is not an issue for normally sized servers, so those memory leaks never got fixed, but for me it was so I started looking for a way to fix them. As oppose to what you may be thinking, not having the source code doesn't make it much "harder" to fix memory leaks. It is just a matter of having the right tools and knowing the tricks