There is no exception to riba (usury). Its forbidden. But there are a few concepts of economics that are not well explained by scholars which are tied to interest.
Historically, the global currency was gold/silver/copper or another metal, and in some cases bartering (i.e. trading apples for oranges). The metal currencies were mediums of exchange and their VALUE could not be altered by anyone.
However, today, metals are no longer a medium of exchange. This currency has been replaced globally by paper currency (or bank drafts), the value of which CAN BE ALTERED by banks, governments and financial institutions. For example, banks create money digitally that didn't previously exist, and in theory, each note issued devalues the currency by a proportionate amount. This devaluing can be seen in annual inflation.
Anybody who lends money in modern day currency, if they want to retain the VALUE of the loan at the end of the term, will have to calculate the total rate of inflation for the term and charge interest equal to the inflation rate. For example: John loans $1 to Ali to purchase a can of coke, in 2009. John wants his money back by 2014. In those 5 years, there was 10% inflation. Can of coke now costs $1.10. Ali pays $1 back to John in 2015 - John suffered a loss and can no longer purchase a can. John should have charged interest at 10% of term.
Similarly, some lenders will charge interest just to cover inflation costs, not for profit. I am not a scholar but I believe this type of "interest" is not usury. But I have not seen Islamic scholars touch on these economic concepts in detail.
Most countries in modern day are debt based economies, with rampant interest and usury that affects almost every aspect of a citizen's life. Meaning, if you try to break free, you will appear to suffer some degradation in quality of life. Most affected by it are the middle and lower income classes, whom rely on loans just to drive a car, get a house or education.
Many economists and bankers themselves will tell you that interest as it exists today is what causes income inequalities, social inequity and oppression which I believe is why the practice is forbidden, not only in Islam but in most religions. So when you lend or take such loans, you are perpetuating the practice and its proliferation in your community, even if you believe you can derive some benefit out of it.
Many Muslims who are perpetually stuck in these practices, they cannot see a way out. They will say "its impossible" to avoid usury. This is essentially the same line of thought employed by drunkards and drug addicts. When you accept this line of thought, you are basically accepting that Allah ordained for us that which is impossible; whereas Allah says "Allah does not obligate anyone beyond his capacity" [Quran 2:286]
From here on, it is a matter of faith; do you have faith in Allah's words or do you believe Allah has gone against his word and ordered you to do what you deem impossible?