mmm but basically people look for big loans like 50 BTC , most of people iwll borrow small amount small amount till the one need the loan gets the full amount , let's say who need the amount is from Africa & the borrowers is from Asia , Europe or America or Australia and he don't give them back their money and walk away ? they will use Interpol or what exactly ? I mean how in the world they will sue him for not giving back their money ?? 
So unless borrower and who need the loan are from the same country or continant the borrower is screwed ? not very cool if you ask me
The avg loan on btcjam is no way near 50 btc, its a much smaller amount. There is debt collectors firms that operate internationally in basically every country of the world, there is no reason why they shouldent be able to collect on a loan that has been taken out in bitcoins, its no stranger than if a person in the UK is taking out a loan in Euro for example so a lender could use one or several of them for collection on debts out of there own country. A lender could also sell off bad debt notes in borrowers in countrys far from themself and buy up notes in borrowers loan in there own country or surrounding countrys and take those debts to court if necessary. The best would of course be if the debt collection process would be handled centrally by btcjam and debt collecting firms working together with them. So unless borrower and who need the loan are from the same country or continant the borrower is screwed ? not very cool if you ask me