Supposing I am working on a long form film (docu or feature), it is easy to select an entire scene in FCP7 and delete or reposition it across layers and tracks...
Normally a clip is connected for some reason to a clip the primary storyline. If you want to move the connected clip, it just moves without affecting other clips. If you want to move or delete the primary storyline clip, the connected clip goes with it.
If you want to move or delete a clip in the primary storyline without affecting clips connected to it, you can first change the connection point with OPT+CMD+click.
If you want to delete the primary storyline clip but not close the gap you can do SHIFT+Delete which leaves a gap clip in its place.
As Tom said you can also use the position tool (press P) which will allow moving clips in the primary storyline without magnetically closing the gap. It will leave a blank or gap clip in its place.
Here are some more tutorials on using the magnetic timeline: