>For example , someone has a great idea for a site, picks up a basic PHP book, reads all of the "advice" on PHP.net and hacks it all together with a few copy and pastes from various coding forums.

You mean exactly what happened with CDBaby, the site the author of TFA created, which became a highly successful business?

Is that a bad thing?

As for the lax security thing, we have seen this too many times in supposedly big and respected web services to be particularly fearful of a newcomer. (Not to mention that the same risks to users that happen by accident by some newb programmer, can also happen by intent, by malicious companies putting up fake businesses and such. People should be vigilant in any case).

There are a couple of answers I can give here:

1) When the company grows large enough, it will hire people and fix this. If it's small, it cannot do damage to many people anyway.

2) The most important services (credit cards and such) are in most cases delegated to third parties anyway (Paypal, Stripe, etc).