I feel like a bit of a fraud with this exercise because I always seems to be 'standing back'. One of my favourite leisure activities is to shoot passers-by with a long lens - my 70-200mm f2.8 being the preferred weapon. I do also sometimes use a 70-300mm but this can only open to f5.6 when on full zoom and is often a bit too close anyway.
The big set-back with this of course is people and cars blocking the 'perfect' shot. I have dozens of throw aways due to my speedy husband straying into the frame. I have found also that sometimes the shallow depth of field can be too distracting. If a certain part or too much of the image is out of focus, even if the subject is very sharp, I find it can ruin a composition. An example is the image below. Although it is not very large in the frame, the bin in the right hand foreground is too distracting. It gives the impression that the viewer is hiding or stalking - not a comfortable or satisfying image.
I like the intimacy of being able to get close to the subject without them noticing - it provides a frisson from the close contact without any kind of self-consciousness. I also like being able to isolate the subject so the images are quite clean. This style has always appealed to me much more than messy wise-angle street photography although I am trying to be more open-minded about this.
The three images below sum up the joy (and the downside) of long focal lengths for me. The old chap has no idea he is being photographed but we can look at the pictures and imagine what kind of person he is, what his home looks like, how he interacts with the world. Unfortunately I could not shoot without a railing being in the way which I am disinclined to crop out, as this would ruin the balance, but which I find to be a negative part of the capture. It is also sometimes tricky to avoid the subject being at the dead centre of the frame as focussing has to be quick with these moving targets.
It is actually quite a dramatic editorial decision to zoom in on a person and cut out their surroundings and their interaction with it. Great for people with very interesting faces or quirky clothes but possibly less so when just capturing the ordinary 'man in the street' and it can sometimes feel too sanitised and controlled.
I get the impression that really talented photographers can allow the surroundings to be left in shot and the isolation of the subject and the intimacy is still there but through killer composition or a very specific use of lenses and correct aperture.