In reply to Dan Cameron (@dancameron).

Dan, just like you are not questioning my intelligence, I'm not going to question your knowledge or your willingness to lie.

Let me start with some facts before going to the 2 points of contention here:

Fact 1: This kind of a plugin is not a necessity for a site to run, is is just a luxury, since there are many offline tools to create invoices.
Fact 2: Once you start storing personal data on any web site, you are painting a bigger target for that site to attract hackers.
Fact 3: WordPress is the most targeted platform by hackers.
Fact: Any web site is hackable, there is no such thing as a safe site, just like there is no such thing as a perfect software.

OK, now let me discuss your objections to my initial points:

Server Resources: Even if your plugin's footprint is minimal, and even if I'm on the most powerful web server, there still will be some slowdown. As far as search engines go, speed is one of the most important factors, so even 1 milliseconds matters. Would I risk my ranking for a plugin that I can really do without, specially when there are tons of other offline solutions? - the answer is simply "no way".

Security: You painted half the picture here. So let me paint the whole story, and let's see what you can come up with:

I do believe you when you say that this plugin conforms to all WP coding practices, and has no security concerns. But that's not the whole story. From the facts, I already established that WordPress sites attract more hackers, and storing personal data will make things even worse. No matter how safe your plugin is, there are still very good chances one can hack the site due to:

1. A hole in WordPress itself. WP is never safe - they released WP 4.0 yesterday, they will release security fixes within 2 weeks - they always do!
2. Themes
3. Plugins
4. The server is not setup properly.
5. A dishonest employee from the hosting company, can walk right up to the server, and steal all your private data.

All I'm saying, by using such plugin, I'm making myself a bigger target for the hackers, and possibly my search engine rankings might suffer - which is not necessary, since I can always use another offline tool.

I hope you now understand my security concerns.