Post-2008 (i.e., the final turning point re: the IRS was when the former UBS employee spilled his beans, but I'd be willing to bet Swiss cooperation post 9-11 just by some heavy-handed Homeland Security Agents in poorly tailored suits storming in discourteously) even grandfathered numbered accounts have no security in them for foreign nationals. As I understand it, if you're an MNC you transfer price and lodge your funds in the most tax-friendly domicile (Ireland) and retain those earnings without any remittance. For US nationals, the best way to engage in tax avoidance is to play a game of seashells in the Seychelles (oh god I'm sorry for the pun) with shelf-companies and auxiliary signatories, and keep on routing around until you eventually land up in HK. The only thing a US citizen gain from a Swiss bank account from is protection domestic civil litigation, i.e., divorce claims. Swiss nationals, as I understand it, still retain their anonymity but who really knows.

Fun fact: It's not the Caymans, Switzerland, or HK that is the largest tax shelter in the world - it's the US banking system.