FRAMING THE PAIR AND GROUP WORK PROBLEM
The "better to have loved and lost" rationale really doesn't apply to attempts to execute pair work and group work activities correctly. There is a lot of other very meaningful work that you can do with the students. Do pair work only if you think it's likely to succeed.

ME:  "That full-class brainstorming session was going really well, why did you cut it off?  Why didn't you let it breathe a little more?" 

TEACHER:  "I needed to move on to the pair work activity."

ME:  "Why?"

TEACHER: "Because otherwise I wouldn't get to it."

ME:  "And you need to get to it because ..."

TEACHER:  “Because otherwise the class is too teacher-centered.”

ME:  "Giving the kids five to ten minutes of mostly talking to each other in Japanese is optimal because it's less teacher-centered?"

TEACHER:  “Yeah ... I agree ... the pair and group work portion of my lesson rarely goes well.  That's a problem.”

ME:  “So why exactly do you do pair and group work?”

TEACHER:  “Well ... don't I have to?”

No. What you have to do is figure out how to maximally engage the maximal number of students in the project of deepening their understanding of English and deepening their creative engagement with English. That may or may not mean that your lesson will include pair or group work. Pair and Group work are usually worth trying for the following reasons, but note that they almost go without saying....
  1. If you can give the students the opportunity to use the language creatively, then that is good.
  2. If you set up a more authentically premised activity where the students speak in order to express ideas rather than in direct response to a teacher's prompt, then that is good.
  3. If you create opportunities for the students to take initiative and own their own learning, then that is good.
But pair work is difficult to run successfully, and when it doesn't go well, vast swaths of potential learning time are lost.  The "better to have loved and lost" rationale really doesn't apply.  There is a lot of other very meaningful work that you can do with the students.  So here are the circumstances under which it would be better to have done something other than pair or group work.
  1. If the groups or the pairs take any more than one minute after the word "go" to figure out what they are supposed to be doing, then you are wasting valuable time.
  2. If during the activity, they spend any less than 90% of their speaking time in English, then you are wasting valuable time.
  3. If during the activity, there is only a half-hearted effort to speak in full, grammatically correct sentences, then you are wasting valuable time.
  4. If during most of the activity, the students are reading off of a paper, then maybe you are not wasting their time, but you should make sure that you are building towards the students being able to utter English sentences without reading off of a page.
  5. If the students are speaking without any effort to use Authentic Rhythm, Melody, and Pronunciation, then depending on the students' current aptitude, you are probably wasting valuable time.
In subsequent posts, I will highlight some possible strategies for making pair work more effective.