Sure, the break-in period is really there, no doubt about it with my speakers (although quite old now, but I do remember quite vividly) and with all other speakers I have seen from out-of-the-box condition at places of friends and family.
However, from posts above (especially venkat's and odyssey's) it seems you got to do it in some specific ways. May be you do. I know some special CDs are available for breaking in CD players (and perhaps also amps) with continuous playing.
What I have always done with whatever I have bought (including any cables), I just use the equipments as usual, be that couple of hours of running every day or whatever at the normal volumes. Obviously the performance is not always great before the break-in. But I wait and things settle eventually. Is there anything wrong doing it this way? I guess not, but one may have to wait longer with certain equipments than the speacialised methods suggested above.
At the same time, I also understand that break-in of electronics and the speakers may be fundamentally very different events. But as I have observed they break in with normal usage over 50 to 200 hours, depending on the equipment. (Elsewhere I have mentioned I have really observed a break-in even for my LCD flat panel TV, the black levels and contrast just improved gradually over a period of a couple of months of normal watching to a significantly better condition than initially).
We all know all cars do break in, although the break-in is mostly mechanical in this case. But one has to maintain certain cautions at this period. Likewise, I thought for speakers to break in, there would be some mechanical elements involved (like vibration of some membrane, although no or negligible friction involved unlike in cars). Just becauise some mechanical parts are involved, I would have thought there should be some caution to be observed like no super-high volumes etc, no extreme high freq for sustained periods etc. But Odyssey above seems to have suggested a high volume. This confuses me a little.
Note added later: The set of my speakers I mentioned above were bought as demo items. However, the sales person told me that they were sparingly used. If I remember correctly, he mentioned something like 30 hours. Now I know all his estimates were on the coservative side. May be actually it had only 20 hours. What I remember is that things (especially the highs) improved significantly gradually over a period of 70-80 hours of my listening to them.