If you want to compare it to something, compare it to regular (snail) mail. It's exactly the same thing.
The solution Dave chose (deleting emails while on holiday) is bad because messages get lost, and it's only caused by his lack of will to NOT check his email every 5 minutes. It completely defeats the purpose of mail.
Imagine disabling your regular mailbox while you go on vacation. What good would that do ?
No it's not. Email occupies the space right in between IM and snail mail. It is way more convenient for me to send email than it is for me to write a letter, and that email sends more quickly. People email you for all sorts of reasons they'd never write a letter. I get tech support requests for Tumblr themes I designed three years ago, and people asking me questions about things I've written, and friends asking me what's up, and lots and lots of email from people at my work. Because the Internet lets me publish without going through a journal or magazine, I receive all the comments that, if I were a traditional columnist, would be going to my editor instead. I'm not receiving as much email as I used to when I kept a regularly-frequented blog, but even so it's weary how much communication I receive.
If I spend a weekend without checking my email, then my flow is disrupted. I have too many messages to respond to them all properly. So I prioritize them and answer many of them curtly or delete some without replying at all. Or, I make an excuse to check my email over the weekend.
If I went on vacation, I'd be incredibly anxious about the upcoming email deluge awaiting me on my return. The temptation to check my email and relieve the burden would be immense. I can sympathize with wanting to disable my inbox until my return.
(The other difference between email and snail mail is that with email you know immediately that your message was not received. With snail mail you're waiting at least two days. That's a frustrating wait. The convenience of email makes it less bothersome when somebody inconveniences your attempt to reach them.)
For many people, email is an absolute train wreck.
The solution Dave chose is bad because messages get lost
This is the point. Dave would say that his solution is good precisely because messages get lost. Dave is effectively increasing the barrier to receiving an email, and filtering out emails that don't reach that barrier, which is an economically reasonable approach to the problem. (This particular approach may not end up being the right one, but it is worth a try.)
If you're really getting that level of email chaff, cut it off at the source. Just throwing out half of it is the Wrong Thing To Do.
Email is a disaster because it lacks flow control. In person, if too many people try to talk to me at once, they will have to wait their turn, and some will eventually give up or move a little faster when they see that others are waiting. Email lacks this dynamic -- everyone gets to talk at once. Disaster.