I have a cousin that used to mine eastern oregon and into northern nevada with a lot of sucess, granted he was an individual, not part of a crew, but there is gold to be found. There are a lot of parts of eastern Oregon that are relatively untouched, majority of the population is in the western 1/4 of the state(where the Hoffman crew all live). Honestly, once you get past Bend (central Oregon), it is more likely to see empty land than homes or land in use. Central/eastern Oregon is high Desert, I am shocked they've even been able to break through some of that ground. The western part of the state is very different, green and lush and has many rivers flowing through, some of the terrain in the Valley is similar to some of the mines in California along highway 49, as well as the parts of Alaska we have seen on this show. The valley has been developed since the 1800s and now, there are less and less sections of mineable land. Not to mention, there are fairly strict land use laws that would prohibit a lot of hobby mining. I wouldn't be shocked if there is gold underground in some of those areas.
The possibility of gold exists, but like has been said, testing should happen, not just "there is visible gold on top of the land" like the Hoffman's found when they were prospecting last season.
Oh, and Todd sucks