Ug. I would advise against using any wallet service to store your Bitcoins. Spend just a few minutes reading the threads on this forum and you will see the bad things that have happened so far. Use either bitcoind or Bitcoin QT (Graphical version of Bitcoin) to store and spend your Bitcoins.
There are many instances where a hosted (shared) EWallet like Paytunia, Instawallet, EasyWallet, or an exchange's EWallet even work very well due to EWallets being convenient and nearly always accessible.
Instawallet and EasyWallet are special case EWallets, where there is no username / password, just a URL. They are referred to as "low security wallets" and are suitable for low amounts.
They don't make great places for storing wealth, but for someone who simply needs an address to receive $5 worth of coins, it works just fine.
I would not trust them even to hold $1 worth of Bitcoin.
So you would have no problem handing your real wallet to someone on the bus or subway and asking them to hold it for you?
There is no insurance backing those services up. They can take your money and other peoples money and run with it as some have done in the past.
Fool me once, shame on you. Fool me twice, shame on me...
If you think the 3 people owning a registered business like instawallet will "run" with a few thousand euros/USDs to ruin their professionnal and social life for good, think twice. Our identities are public if you care to check. Just so you know 90% of the bitcoins are in cold storage and the redemption of a storage key by a single individual is NOT possible under our redemption process.
Without social trust, there is no efficient economy, period, regardless of the monetary system you are using.
To someone younger it might sound like a good idea, but I have learned that trust without insurance is not a good thing and that you will probably get burned.
