Funny you should say that. Exactly my experience. Just left a comment on Adam's blog, but let me add it here as well.

I turned off Dashboard where I had a couple of unused widgets active running in the background (used Dashboardkiller app from MacUpdate) because I haven't used any of those widgets in months. Suddenly all of my mysterious memory/paging issues on Lion disappeared. Swap and page-outs decreased significantly. Machine is running like the first fresh install. Give it a try.

Edit: I'm running Lion 10.7.4

I've never really tried to understand Dashboard from the O/S side, but it seems like it's almost installing a separate WebKit process for each widget.

Edit: I'm on Mountain Lion, and Dashboard is still a memory hog. I just disable it now.

I believe it actually is a separate WebKit process per widget.

Could you quantify the Dashboard memory usage? I'm using the Weather and Delivery Status widgets, and they're only using 16.7 MB and 28.9 MB. This is on Mountain Lion.

edit: most of that memory is shared, so the real memory usage is even lower.

Note: I did not shut down dashboard because of reported memory usage, nothing was obvious from activity-monitor either, ie not listed separately as a memory-hog.

However, once I did shut it down (not just remove all the widgets, I had like 10 running, but actually prevent it from starting) my machine was finally back to normal.

I'd be curious to see if anyone here who does experience the memory problems can replicate this.

Addition: since shutting it down, the reported memory usage for the kernel task has dropped a lot, does that make sense?

My dashboard has 10 widgets, two of those are web clips. I'm seeing 90MB real memory and 220MB virtual. Maybe it's not as bad as I thought. Or maybe it's just improved since 10.6.