Yes, infamy has replaced fame or talent in celebrity culture, because there are so many people who are famous who have not really done anything. Paris Hilton is a good example. The Octomom is another one. These people really haven't done anything, and yet they have major celebrity status in the world.
These days, most celebrities are famous just because they consciously decided to be famous. They do that by any means at their disposal, such as creating and reporting scandals. There is some talent in the pool but not a lot in many cases and so infamy is resorted to just to get some press.
If you look at some of the most famous celebrities they are often the most talented and not infamous in any way. I think some reality stars and infamous stars like Miley Cyrus often rise to stardom very quickly but they also burn out very quickly. The true stars that stay famous are often the ones with true talent.
I do not believe infamy has replaced fame or talent in celebrity culture. Infamy is generally defined as being well known for bad habits or bad deeds. While this may be the case with celebrities like Charlie Sheen, it does not represent the majority. We have many celebrities who attempt to live normal lives.