I am curious: NOS tapes that I bought in the last year
or so came
 with the foam blocks, but I don't recall ever encountering either a
 foam block or the magic plastic tape "back in the day" on tapes from
 the rack that I handled as a backup operator. I presume that if they
 came with blocks, they were discarded when the tapes were
 unpacked. Is it really necessary to secure the tape end in normal
 use, or is it just needed during shipping to keep the tape from
 getting loose on the reel during transport? 
For my money, there ought to be one always, though careful handling in a
controlled environment can probably get away with skipping them.
Shipping is where the worst stresses occur, of course, so is the most
important.  I've received a number of tapes for imaging over the last
few years, and I don't think a single one had anything to keep it
packed.  One such tape had slipped an outer chunk of the pack around the
inner rest, producing a hard crease.  Needless to say, there was a read
error there.
De