He is a liability, no argument possible against that.
The problem is, if he was bagging goals for fun or improving our teamplay significantly, we could bare with it.
The situation is overwise.
Since his signing he's been averrage at most, hardly has any impact when on the pitch, his goal records the last two years speaks for itself.
In fact, i think guys like Anelka, Benzema or Drogba were already better than him at the same age and that he will never reach their level ( let's not even mention Et'oo, Raul, C. Ronaldo, Henry, Ibrahimovic, Inzaghi, Trezeguet ).
Although we will for ever be thankfull for that ultimate final pass on May 2012,
i think we should get ridd of him as soon as possible, before his market value drops down dramatically.