that "unique bit" is all you need to have access to the wallet?
For instawallet yes. That is why it is "instant". Your wallet = url. No logins, no accounts, no usernames, no passwords.
Your wallet is your URL. Your URL is your wallet.
If the content rules/info page is going to recommend instawallet it should include a pair of warnings:
1) If anyone else learns your instawallet URL they can steal your bitcoins (treat it like cash).
2) If you lose your instawallet URL then you have lost your bitcoins (treat it like cash).