What Neighbors

We have lived here for three years now and in that three years in the apartment next to us we have had three different families living there and it has been empty for several months between those families.  Craig and I are beginning to think that there is something going on.  The management claims that there is a waiting list despite there always being empty units.  The apartment at the end of the building moved out after the apartment next to us, but it has been filled already.  Kind of strange.  Maybe we're horrible neighbors.  Our washer and dryer are pretty loud,  the floor moves when the washer is going.  It is kind of like having a mini earthquake every time we run the washer (I'm not joking either.  You can stand in the upstairs opposite corner of the apartment and feel the floor shaking slightly).  Don't get me wrong,  I am not complaining.  It is nice have no neighbors, but now that I have mentioned this I am sure will have neighbors move in and it won't be pleasant.  Here's hoping that won't be the case.  All of our neighbors in the past have been really nice.