Thanks for the replies guys. I guess I am just thinking that whilst the security of having the wallet located here with me at home (and regularly backed up), it would also be nice to be able to use coins from my mobile device, hence a web-based wallet. But I suppose then using such might simply just require the moving of coins between theme before they are utilised.
What about phone-based wallets? Do such things exist? Are they safe?
Think of the PC based Bitcoin-Qt wallet at home as the money in your safe at home, and the web based wallet as, well, your wallet.
You might be comfortable leaving a few thousand dollars in your safe at home, but might become uncomfortable walking around in a large crowd with a few thousand dollars in your wallet in your back pocket.
Before you head out for the day, you'd remove some cash from your safe and put it in your wallet. If you received a large sum of cash while you were out, you might hold it in your wallet until you got home, but would then immediately move it to the safe.
There's no reason you can't have multiple bitcoin wallets. Perhaps a few paper wallets for significantly large sums that won't be used for weeks or months, Bitcoin-Qt for storage of the bitcoins that you don't need immediately, but want convenient access to, and a smartphone or web-based wallet for amounts that you expect to spend while you're not at home.
