Few ideas have received more press, recently, than Social Impact Bonds (SIBs). With support from all sides of the house, this innovative solution is the Government's great hope for bringing about progress and systemic improvements to the way public services are run. However, as a conference in December indicated, there is growing concern that what looks good in theory may not translate to the real world.

The Conference, hosted by the Social Market Foundation, brought together names such as Iain Duncan Smith, Danny Alexander, Chief Secretary of the Treasury, and Toby Eccles, Director of Social Finance, to debate the future of SIBs. What followed was one of the most critical examinations of the value SIBs offer that we've seen to date.

The first question to be raised was of what policy areas SIBs could be employed in, and here there seemed to be some agreement. The first government pilot of the SIBs, deployed in 2010, was put to use to help families in deprived communities, and there were many on hand to suggest they should be used in related areas.

For Dame Clare Tickell, of Action for Children, a key target area should be helping children in poverty. Toby Eccles, agreed childcare was crucial, but also pointed to drug rehabilitation, healthcare and homelessness. However, herein lies the greatest challenge for potential investors. In general, the marginalised tend to be of high expense and low outcome. Investors must be willing to take risks, but according to Tickell, there needs to be more energy in convincing investors that savings will, in fact, be made. According to government figures,  £4bn alone is spent on assisting families in deprived areas. Investors will need assuring that SIBs can succeed in reducing these costs.

Concerns about the value of SIBs were further voiced after the mid-morning break as talk drifted towards the question of scalability for the market. Charlie Green of the Private Equity Foundation brought up the difficult issue of measurement. At this experimental stage, there needs to be a greater understanding, across the board about what data needs to be used to prove its success. As Nick Temple, of Social Enterprise UK pointed out, our sector should be better placed than most to achieve this. Social enterprises are, after all, quite used to measuring multiple bottom lines. However, most still require substantial support to become investment and business ready.

Matt Robinson, Head of Social Investment at the Cabinet Office took concerns a step further questioning the assumption that payment by results provides the answer. There is a sense, he said, that the market (in which the fog is only really just beginning to lift) still has some way to go to prove its feasibility. It is clear that commissioners need to pay more than expected, but understanding the data of cohorts in the same space and the scale of future performance are things that will need to be tackled simultaneously at this experimental stage. For Robinson, this is another massive engagement exercise between commissioners, local authorities and other investment intermediaries who will all need to share data horizontally.

For all the hype surrounding social impact bonds, the road to success still seems to be strewn in potholes. We are left with as many questions as answers: is the Government doing more harm than good trying to micro-manage the problem of public services' efficiency and positive impact via social impact bonds? And most of all, the big elephant in the room: do they actually work? So much hope throughout government and across the social sector has been invested in social impact bonds that we may have reached the point where some refuse to countenance the prospect of failure. Thoughts are being murmured, or be it hesitantly, that the time is coming when we'll be better served looking beyond SIBs at other examples of social investment intermediaries which are demonstrating better success.