None special.
1) Tapes are mechanical and constant reuse will mean several play, rewind , fast foward, pause cycles: less likely to happen if reuse is limited
2) Tapes being magnetic means that constant rearrangement ( by rerecording) of the magnetic particles may lead to less precise info storage nessesary for high quality video ..the so called dropouts will then occur especiallly if previously recorded material is incompletely erased at time of new recording
Having said that, the actual extent to which tape degradation occurs with reuse is far from predictable . Reasosns are probably multi factorial starting with quality ( and therefore durability) of the tape itself.
I would advise not to reuse if the anticipated footage is of a crucial nature but for everyday "video snapshots" it may not prove too bad as the tapes and digital means of recording are fairly robust.
The fact that tapes have become relatively inexpensive and easy to find and that as a means or archiving your original or edited footage they are dependable is why reuse doesnt get much mention.
On occasion when I have run out of fresh tape and need to cary on shooting I have reused tapes with unimportant stuff on them with no regrets
Short answer 
: Reuse by all means just not repeatedly , not as a general habit and avoid for those "special" events
