I have been doing web work for a decade, and I can tell you this happens all the time. In fact, older employees in marketing have told me horror stories about 800 numbers and mailing addresses that were never set up, misprinted, or never updated.
I always tell clients that they should set up emails that describe the job/function, like email@example.com and firstname.lastname@example.org, and make sure that those emails go to a distribution list that goes to at least two people.
You wouldn't believe how often critical accounts and webforms are only accessible with the email addresses of Sally the Secretary or William the Webmaster. When they leave, no one knows there is a problem, until it is a big problem.
Now in big commercial operations, especially web sites, there are large QA departments...
HAH! Ah, hah, hah! Hah, hah, hah, hah, hah. Hee.
Wait, wut, where you serious?
It's only a matter of time until a private company provides this service.
I thought of doing this years ago.
At the time, I imagined paying people to install cameras in vehicles, and selling access to the database to law enforcement, employers, spouses, etc. Now, that probably isn't necessary. The company could just scan the millions of photos and videos that are posted publicly every day.
If some company isn't already experimenting with this, I would be amazed.
In the end, this will be done, either by the government or a company; probably both.
I spent days researching a sub-string problem like this six years ago:
'If you're under 40, you've not seen this stuff before.'
I'm 43, and I've seen it. I was on top of Mt. Lincoln in -50 degree wind chill in late November more than a decade ago. There was a tiny gap between my facemask and my ski googles, and I got 2nd-3rd degree frostbite on a small part of the skin on my cheekbone in less than an hour. I still have some nerve damage there.
The danger to someone who isn't prepared is very real.
1. Do you offer a specific Drupal distribution that you manage, or do you just give the customer a LAMP stack and let them set up Drupal any way they want?
2. How much do you charge?
Drupal can be set up to be extremely scalable, but someone has to do that setup.
If you offer a Drupal distribution and it doesn't scale, that is your fault. If making it stable and scalable is "too much work", charge more.
On the other hand, if your customers are setting up Drupal by themselves, then it isn't your problem if they don't set it up correctly. If you don't want cheap customers that hire cheap agencies, charge more.
I know this sounds glib, but you wouldn't believe how often I have seen talented people bogged down with problems because they simply weren't willing to ask for the money they were worth. Higher rates = more money = less clients = less work. It may seem scary, but if you really are good, the good clients will stick with you despite the cost, and the problem clients will go be a problem for your competition.