Even though AMD is the proud owner of multiple chipset lines, including their original chipsets along with the Radeon line, they actually have a minority share of chipsets for their own platforms. According to recent research, it is actually Nvidia who will be found sharing space with most AMD processors. More than 60%, in fact.
This figure has remained steady despite AMD's chipsets like the AMD 7 series helping them make a comeback, going from 26% to 37% in the past year. The share AMD has won has largely come from SiS and VIA, it seems. It's interesting that one of AMD's biggest competitors is the chipset of choice for their processors. If recent trends are an accurate depiction of how this will change, AMD should gain share pretty quickly.
Not all of that is good. If AMD manages to overtake Nvidia in this market, Nvidia may choose to focus on Intel CPUs. Ultimately that could lead to a vendor lock, with Nvidia being paired only (or largely) with Intel, and AMD relying on their own CPUs, GPUs and chipsets.