PSU4life: It's not about being sued, it's about jailtime for fake pharma.
Others are just cases of it being a generic that's marketed as the brand name.
I can't remember any off the top of my head, but I'm certain it's happened because I remember articles in the paper of people in Queensland getting some serious jailtime for pushing chalk instead of viagra.
If you're promoting a legit pharma affiliate, so long as you don't make false claims, you should be fine... Just research them a little bit, and ask your AM some questions about them.
Terms like "win" and "free" have certain limitations. To win something, there must be competition, in which case, there is a discernible chance of not winning (aka losing). Therefore, if you say "Win an X", and they don't win it, they are in the pool of non-winners... in legal practice, there MUST be a winner to all competitions, but who says that can't be you

Go buy yourself that $500 giftcard, bam, you're the winner. (Heh, the number of door prizes I rigged at the nightclub I used to run on that loophole).
With the use of the word "free", it doesn't haven't to pertain to the entirety of the service. If ANY of the service is free, sales puffery laws allow the use of the term in England, Australia, and all states that I know of in the US. Interestingly enough, in NZ, what is free has to be documented somewhere.
In any case, there ARE tons of lawsuits if you look up the public documents about it. Most of them are settled out of court with a silence order attached though.
[EDIT] Found one of Microsoft and Pfizer taking down some spammers:
Q&A: Pfizer and Microsoft Strike at Alleged Spammers: Three of the chief investigators tell how Microsoft and the pharmaceutical giant came to file lawsuits aimed at shutting down spam rings allegedly pitching illegal and potentially harmful Viagra k