Pagination, Sets, Checkboxes

When I was at RailsConf2008 I learned a lot about life and Rails but there were some nagging problems that lingered after me for a long time. At one point in the talks there was a discussion of how to make listing pages have checkboxes and how to handle this data. The problem is complicated by pagination and filtering so it's actually a really good problem to talk about. The proposed solution was to send back a structure that looked something like this:

[{:id => 1, :activated => "+", :contact => "-"}, ...]
At this point I was probably playing pogs in the audience with Ryan Schenk so the details are lost to time but the concept remains. It seems needlessly complex though. A very interesting idea, no doubt about it, and it certainly has its merit but it seems very complex to me when we're talking about booleans. Also, I feel like it's worth mentioning that this method is much faster than the below method but somehow that doesn't turn me off that badly. Instead of the above I took the already well accepted practice of using the check_box_tag in the view with the addition of a hidden field which would tell me which objects to care about:
<% @users.each do |user| %>
  <%= hidden_field_tag('seen[]', -%>
  <%= check_box_tag 'activated[]', -%>
<% end %>
In the controller it's as easy as loading up params[:seen] and loading each object:
def index
    activated_ids = params[:activated].collect {|id| id.to_i} if params[:activated]
    seen_ids = params[:seen].collect {|id| id.to_i} if params[:seen]

    if activated_ids
      seen_ids.each do |id|
        r = User.find_by_id(id)
        r.activated = activated_ids.include?(id)
So what I don't get is whether this is wrong on some moral stance or if I really didn't understand what the presenter was getting at. Yes, he loads and saves fewer objects, which could be important. But he also introduced what seems to me to be a lot of complexity into a fairly simple process. At any rate, this code is here in case someone needs to find it until I find what the presenter was proposing. I seem to recall being impressed at the time so there must be something I've forgotten.