IB - interactive broker, an international security house based and listed in US. Similar to the security house in HK but it provide full range of product coverage cross asset class, region and derivatives. As it is on electronic platform, the charge is relatively cheap. Also, it provide API to allow you to trade in your excel spreadsheet. So it provide a wider flexibility for you to trade. Eg: you can do some rule based trading, define stop loss trade, profit taking trade etc. As it is security house, the regulation on it is less strict, so you can imagine there is higher credit risk (margin ac).
PB - refer to private banking. you can imagine it is a banking ac higher level than premier / citigold. It provide full range of banking service including bond ipo/derviative trading like NDF, swap etc and it provide you personal banker for the advise service. The famous PB are the ones from Switzerland like UBS / CS.
Put it simple, there are two kinds of so called "lehman minibond"
(1) Bond issued by Lehman Brother: Lehman default, bond payer will get paid based on recovery rate.
(2) Credit Link Bond issued by other entity: The idea behind is there is option component in the bond. The bond arranger sell a option to get the premium and use this premium to increase the bond coupon. The option is that "you" have to pay when Lehman is defaulted.
To avoid (1), it is difficult as you never know when a company is defaulted. The credit rating from credit agency is not that realiable. We can try the best to avoid by doing more background check on the company. Also need to know the feature of the bond. When a company default, the bond holder will be paid based on the rank of bond they hold.
For (2), it should not be allowed to sell in retail after minibond and not sure if you can buy via exchange. To avoid it, you can read the coupon of the bond and term to see if there is any special clause.
In short, the market is perfect most of the time. High risk high return. Higher yield must need you to take higher risk. Just the matter if you know it and if you are willing to take. Minibond story is investor bought it without knowing the potential risk. If they know it from day 1, they should 輸得心服口服.