Sorry, the roundup e-mail interface ate some lines of code:

>>> b = b''
>>> sys.getrefcount(b)
30
>>> m = memoryview(b)
>>> sys.getrefcount(b)
32
>>> del m
>>> sys.getrefcount(b)
31

It doesn't happen with bytearrays, so I suspect it's that you only
DECREF when releasebuffer method exists:

>>> b = bytearray()
>>> sys.getrefcount(b)
2
>>> m = memoryview(b)
>>> sys.getrefcount(b)
4
>>> del m
>>> sys.getrefcount(b)
2