Is this a harmless poll or the grass roots being sounded out?
Previous Lib/Lab coalitions are, in my opinion the main reason why the Lib Dems are still the third party in British politics, as when things get bad for Labour the Lib Dems jump in. By accepting coalitions in the past they have sewn themselves into the position of the Third Party.
Should the possibility arise, I hope the Lib Dems take their chances and try to overtake Labour in the polls instead. Thing is, I really do not anticipate there being a hung Parliament now, the time and opportunity to fight for that has now passed Gordon Brown by. In my opinion, it is damage limitation from here on.
Also, In a hypothetical situation I suspect Vince Cable and Ming Campbell would be in favour of joining a national coalition, but I do not see Nick Clegg coming on board, so such a move could split, possibly terminally the Liberal Democrats.