Seek sought to raise A$125 million from retail investors and lost up to A$0.5 million in the process. This is how much the legal due diligence involved in the preparation of a 124-page full prospectus is likely to have cost the company (not including management time). Seek pulled its "subordinated notes" issue on Tuesday. A tersely worded statement to the ASX simply said that Seek would not be proceeding with the issue announced to the market on 4 June 2012. In other words, the book build that was slated to take place last Friday, failed. But why did it fail?A common excuse given for the failure of a book build is market conditions. This explanation can sometimes be hard to dispute but more often than not the true reason for failure lies with the issuer or the structure of the issue.Seek itself is unlikely to have been a cause for concern. Its online businesses are sufficiently diversified, in terms of geography and sector, to have been unlikely to be a concern. Moreover, its recent performance has been strong and improving. This is reflected in its share price, which started the year at around A$5.70 and closed ahead of the ASX announcement at A$6.66.The structure of an issue is reflected in its terms and conditions, and its pricing. That the issue was the highest yielding hybrid to come to the market so far this year was acknowledged in our write-up last week, along with the fact that this should ring alarm bells.This was the most aggressively structured hybrid yet seen. To call the securities being offered subordinated notes was misleading, maybe even grossly so.These securities were definitely hybrid securities, with all the risks of equity and none of the upside. The only 'debt-like' features were the potential for a fixed coupon payment to be made and the possibility that the securities might be redeemed at face value after five years.But the payment of coupons and the repayment of principal were to be at the sole discretion of Seek. And, unlike the other hybrid issues that have come to the market this year, there was no time limit on the recognition of 'equity credit'. For Seek, the 'equity credit' obtained from its auditors and bankers would be perpetual. It seems most likely that the aggressive structure of the issue was recognised by institutional investors and even the brokers that would have sold it to their retail clients. However, it is possible that conditions in the market have changed to such an extent that debt securities in general have fallen out of favour.Banking Day noted last week that the Tatts issue appeared to be struggling, and while by all accounts the Heritage Bank senior bond issue launched prior to the Tatts offering was well oversubscribed there is yet to be confirmation of this. The Heritage Bank issue closed on Tuesday and the Tatts issue will close on Monday week.