What happens to my bitcoins if lose my wallet file e.g. I suffer data loss and my computer is unrecoverable? You run bitcoin as a service on your local computer.  What happens if this computer is compromised?  A corrupt/failed hard drive or theft leads to the machine being lost and unrecoverable, and my bitcoin details (addresses etc) are gone.  Do my bitcoins disappear into the ether?

i.e. What happens to my bitcoins if my wallet file is compromised/lost?
If a wallet file is truly lost with zero ability to recover it, then the coins it contained are lost forever.  Think of it as cash left in a burning house.  

Be sure to periodically backup your wallet.dat file.  It is best to also encrypt those backups lest they be compromised giving someone else access to your wallet.