Looking at his record on baseball-reference.com, he's struck out more than 100 times once (102), as a 21-year-old rookie with the Pirates. Further, he has had more walks than strikeouts EVERY YEAR since 1990, well before the drugs. Giambi, on the other hand, has had only two years (2000 and 2001) when he had more walks than strikeouts. And McGwire's stats on the BB/K ratio isn't a lot better.
And that Red Sox slugger I noted earlier STILL had his great eyesight well into his 50s, when he was managing the Senators/Rangers. Some people just have good eyes, and Bonds just seems to be in that category.
That's not to say what he's done to himself with whatever he's been ingesting didn't help in other places...
One potential issue with a player's BB/K ratio is that it is only an accurate indicator of a player's batting eye and selectivity if you eliminate intentional walks from the mix. I suspect that Bonds has had an enormous number of intentional walks -- particularly in more recent years.
Giambi strikes out alot, but he's one of those guys whose statistics look bizarre in some ways. He only hit .271 last year, but actually led the AL with a .440 on-base percentage. I know he doesn't get walked intentionally very much -- especially in a lineup like that in New York.