Among the topics canvassed in a session at the Australian Financial Review Banking and Wealth Summit on market risk for Australia's major banks was the apparent conundrum posed by Macquarie Group and its "junk bonds" investments. As has been discussed at length by columnist Christopher Joye in the pages of the AFR in recent weeks the Macquarie Group has been investing in high yield fixed income assets - colloquially known as 'junk bonds'.Moderating a panel to discuss the view on risk from sell-side and buy-side bank sector analysts at the Australian Financial Review Banking and Wealth Summit, Joye raised his concerns that, with default rates at five times major bank levels, and home loans arrears running at multiples of major Australian banks (all the while benefitting from the Australian government's implicit bank guarantee), the danger was that Macquarie was pushing its luck too far.Being deemed a Domestic Systemically Important Bank gained Macquarie two extra notches from the rating agencies. This gives Australia's largest investment bank access to less expensive funding and capital.Paul Taylor, country head of equities investments at Fidelity International, was more circumspect than Joye on this point, noting that investment banks were "opportunistic, whether it''s looking for an arbitrage play or a very event-specific deal."Taylor also said that most of the criticism of Macquarie had been because they've followed a high-risk investment strategy and been successful.JP Morgan banking analyst Scott Manning refused to comment in detail on individual banks. Taking the sector as a whole, he observed that Australia's majors were not able to chase yield offshore, but in Macquarie's case 60 per cent of group revenue was generated offshore.Taylor agreed, adding that Macquarie had to "demonstrate consistency in this strategy to the market, or its share price will fall."Interestingly, none of the panellists would be drawn on whether this assessment of Macquarie's business model meant it would achieve a much higher return on equity in the 2016-17 financial year.