Musically Jumping The Shark

The last Black Eyed Peas album triggered this, although I reckon there is a case for "The E.N.D" as the album that did it for them, despite it having two of their highest selling singles (I Gotta Feeling and Boom Boom Pow).
Which album signifies the beginning of the downward turn for a band? I have always had U2 in my collection, but for me, "No Line On The Horizon" was a no-buy, as nothing I heard on it "grabbed" me like the rest. For many bands, their "shark jump" can often be traced to one particular album (or for some acts, the debut album), but interested to know which LP's are considered "The Shark Jump" for which acts.
Which album signifies the beginning of the downward turn for a band? I have always had U2 in my collection, but for me, "No Line On The Horizon" was a no-buy, as nothing I heard on it "grabbed" me like the rest. For many bands, their "shark jump" can often be traced to one particular album (or for some acts, the debut album), but interested to know which LP's are considered "The Shark Jump" for which acts.