Apple added an anti-phishing feature to Safari in the 3.1 release. Called Fraud Warning (it's in Settings->Safari->Security), the modification was released with little fanfare (or explanation), and it appears that there may be confusion about how it works.
Computerworld reported on two anti-malware researchers who had taken a look at users who had implemented the feature and found it gave inconsistent results with known malicious sites. On Wednesday, Michael Sutton, the vice president of security research at Zscaler told Computerworld "[i]t was blocking nothing." On Thursday, he said, "it started blocking some sites, for some users, but it was inconsistent. Some sites are being blocked, others are not."