Safe sex is a joke. My uncle is a doc who has been practicing in Marin County for over 30 years, and he has seen it all. Just about everyone in those ads puts HIV-, safe, discreet, disease free, etc. Then when they meet the guy and thinks he looks okay, so much for safe sex. Or they use condoms maybe the first 2 or 3 times and figure they guy looks healthy, so they chuck the condoms.
Have you read some of the posts on here by gay men who live in the S.F. area? They are not practicing safe sex.
Look at this PDF file.
http://www.dph.sf.ca.us/PHP/RptsHIVAIDS/qrtrpt062007.pdf
Just about every table lists gay and bisexual men at the top of the list. If you look at the chart the green line shows persons living with AIDS. Yes there are more people living with AIDS due to medical advances.
If you look at the red line you can see there are fewer deaths due to medical advances. The blue line shows the decrease in cases but doesn't explain the full story. S.F. is a city where people come and go. More and more gay men move into that city every year. Not everyone is tracked. Not everyone has an HIV test. And many people who are HIV pos don't even know it.
All that means is that they expected more cases than what there are. It's no different than saying we expected 5000 people to die on 9/11, but it was an overestimate and it turns out only 3000 died.
The article states:
"The reasons for the apparent decline in new HIV infections may take years to understand, but Katz said the most likely explanation is that effective AIDS drugs have lowered the level of virus in those men who are HIV-positive and still having unprotected sex."