Will the Liberals' decision to give preferences to Labor put an end to the Greens' chances of winning seats at this election? Tim Colebatch in the Age (15/8) argues that Adam Bandt still has a reasonable chance of retaining his seat of Melbourne and that the Greens could hold their own, or even improve their position in the Senate. 

He explains this as follows:

... if Liberal voters direct preferences as they did in the 2010 state election – the last time the Liberals told their supporters to put Labor ahead of the Greens – Bandt could hold his seat if he can win a swing of just 4.2 per cent from Labor.

And in the Senate, the Greens have won 14 Senate contests since they began, but only one through Coalition preferences – ironically, when former communist Lee Rhiannon won in NSW in 2010.

Why don't Coalition preferences have a bigger impact? Three reasons.

First, there are only two seats where they are likely to be distributed – Melbourne, and the inner Hobart seat of Denison, held by independent Andrew Wilkie. ...

Second, inner city voters are independent types. A study by the Victorian Electoral Commission of voting in four inner city and four country seats at the 2006 election found that fewer than 50 per cent of voters followed their party's how to vote card.

[And third,] ... history shows Coalition preferences rarely make a difference. Of the 14 Senate seats the Greens have won since 1996, only one was decided by Liberal preferences.

Read more here.

Nick Economou - see video here - argues that the Liberal preference deal will make it difficult for Adam Bandt, but argues that it's ALP preferences which will be more influential for the Greens. There are rumors that the ALP may do a deal with the Katter Party in Queensland which would secure Katter the final Senate place ahead of the Greens. 

However, in Victoria, ALP preferences may help get Greens candidate, Janet Rice over the line. Read more here