They were still checking bags in 2010.
There's a covered area by the gates of the park with tables where they have a quick look in your bags.
It's been far more strict since around 9/11 though. There are no public lockers in DLRP (well there are but you can't use them as they could be used to plant a bomb). I was told that was the reason at City hall as I used to keep my insulin in there - nice and cool.
In the early years, they were looking for food (you had the choice of either giving it up or eating it in the picnic area just outside the park). This was in the days when staying at one of the hotels did NOT include any food or drink. You had to buy breakfast at the restaurant.
It was in 1994 that they first gave you a continental breakfast. There was a trolley with a coffee urn and some croissants in the lobby on each floor (only one croissant each) - and this was the Newport Bay hotel!
The following year, you got a decent breakfast (cereal, ham slices, cheese slices, various pots of fruit puree or yoghurt and bread rolls or croissants - which people started to fill their bags with to take into the park). The search for food seemed to stop then - apart from hampers and obvious picnic stuff. They started to allow in cans of Coke and sandwiches within reason. Rule of thumb seems to be "if you can eat/drink it whilst walking, it's OK. If you need to sit down and eat it, it's not". There were a few years when they stopped searching everyone and just picked you out at random for a spot check. As I said, since 9/11 everyone gets their bags looked in (usually it's just open your bag and let them look into it rather than a search unless they spot something unusual and then it's all out on the table for all to see) . Yes, it's a pain as there is no line for "no bags". I'd say that 1995-2000 were "just walk in" times unless you had large bags or drew attention.
Now, on saying all of this, we have lived rough by staying at the Disneyland Hotel for the past few years (2008/09/10) and guests there don't go through any checks as they are already through the main gates so can't speak for those years but I'm sure I saw the tent covers. . Definitely had checks in 2006 though in the August.