I don't know about you, but I spend approximately one third of my awake time at work. One third of my conscious life. I'm going to make sure that I enjoy that time, and having enticing colleagues has a lot to do with that in my experience.
There are tons of interesting, very professional people around. There's no need to stick with the boring ones you find along the way, so yes, I would also avoid them.
If there's a glut of otherwise equally qualified people, sure. Is that the case with programmers?
An otherwise boring guy who goes home to his family and spends his weekends working on his house and watching football might get you one week closer to shipping product than the guy who goes out for drinks after work and will play video games with you and go rock climbing. So if you don't hire him, your competitors will and then your competition will leave you behind while you're out drinking and playing video games and rock climbing.
Why do you link "enticing colleague" with "doing whatever with that guy after (instead of) work(ing)"?
So your competitors hire the boring guy and get that feature one week earlier. You hire interesting people and they form a cohesive team, carry each other through tough times and work more passionately overall. At the end, you get N extra, unique features as a byproduct of your more involved workers, shooting months ahead of your competitor.
I know I presented an ideal case, but it makes my point. Working around boring (as in non-interesting) people is boring, and you won't be as productive in that environment. Thus, it makes sense to avoid these people unless you very much need their specific skills and you can't find those anywhere else.
I guess you'll just have to define what you mean by "boring" then. People who can meaningfully contribute to solving problems are good programmers and good professionals, but they could still be "boring" in the sense that they're not interesting as people.
Let's say you had a coworker who was knowledgable about the problem domain you worked on, produced lots of good code, made great positive contributions to any design meeting or code review he was invited to, always had a free moment to answer questions, but he always brought leftovers from home for lunch and ate by himself and never really made a joke or hung around with the team in a social context and you never got a sense for what his personality was outside of work because he only ever seemed to get engaged when the discussion was about work. I'd say that's a great coworker, someone I would love to work with, but also a very boring person. So why wouldn't you want to work with this guy?
Obviously, I would prefer to work with this guy than with someone more interesting but clueless. However, this doesn't mean that I would be happy doing it.
On the one hand, you present a very idealized case: how can she engage in (tangentially) work-related discussions if she's never around when discussions happen outside of meetings? After 8 years in industry and 4 as a PhD student, I have worked with and around many excellent people. However, I still have to meet someone that fits your example. They probably exist, but it is way easier to find either excellent interesting people or excellent boring people who simply won't get as engaged in your team/company.
On the other hand, at least for a small company, hiring the wrong person is much more costly than passing on a good candidate. Thus, when you interview (hopefully excellent) boring persons, probabilities are hugely stacked against them.
The point of my example was to isolate "boring" as a trait to demonstrate that, all other things being equal, "boring" doesn't matter. If someone's boring and also an asshole, the problem is that they're an asshole. If someone's boring and also doesn't contribute ideas, then the problem is that they don't contribute ideas. And so forth. The actual problem is never that someone is boring.
Personally I wouldn't mind working with him as a fellow employee, but he'd make me nervous as a manager of a small business. He sounds like he's great at his job, but has zero emotional ties to it, which translates to him being less likely to weather any bad times the company may face.
Ultimately, you clearly agree that gaining and retaining great talent is what makes a software business stand ahead of its competition, so isn't it risky to gain someone who isn't going to feel bad about leaving the business (and take all his experience with him)? If I can hire someone who'll fit in well with the team and produce good quality code, then I'd consider him a better long term investment that someone who fits in poorly with the team and writes great quality code, purely because the latter person has fewer reasons to stick with the business than the former.
I'm not sure what kind of connection there is between being boring and being more likely to jump ship. Plenty of interesting people jump ship too, because the best way to become interesting is to accumulate a lifetime of diverse experiences and staying in any one place gets in the way of that.
If you don't want people to leave the business, earn their loyalty. A boring person still wants to be treated fairly. They still want to take vacation, even if it's to visit their boring family rather than go backpacking in Tibet. They still have the same capacity to either enjoy or hate their job. They just don't necessarily have an interesting answer to the question "any plans for the weekend?", and I don't see why that makes them worse employees.
I'm not sure we mean the same thing by 'boring'. Boring, to me, doesn't mean that the person doesn't have hobbies, rather it means that the person is a perfectly nice person who just doesn't gel with the team. In fact, 'boring' is probably the wrong word here: it should probably be something closer to 'outsider'. That said, larger organisations do depend upon outsiders to prevent groupthink, so this is a multi-faceted issue.
There are tons of interesting, very professional people around. There's no need to stick with the boring ones you find along the way, so yes, I would also avoid them.