And anyone who's been in a security line knows that they're slow NOT due to people putting 2 bags on the conveyer to be x-rayed instead of 1, but waiting for people (who've been in line for 30 minutes) who wait until they're at the front of the line to decide to empty their pockets of phones, change, belt, etc. etc......as if the requirement to do so was sprung on them as a big suprise.
In all seriousness here is a suggestion for how to speed it all up, 2 bags or otherwise (and that was the excuse for that policy, incidentally).
Before you get to the screening *queue*, provide a supply of thick-ish re-usable (for environmental purposes) clear plastic carrier bags, plus the toiletries bags if practicable. Provide a row of tables at this point, a floating member of staff for advice and a set of notices roughly thus:-
"Remove your shoes and place in one clear bag. If you are wearing a coat remove this and place in another clear bag. If you are carrying a laptop or other large electrical equipment, place this in a third bag. Place all items from your pockets in a fourth bag. Present all these bags plus your one carry-on luggage item to the security screener at the X-ray machine. Anyone not complying to this notice, or anyone found with non-permitted items as shown, will be refused security screening and will be told to return to this table to complete this then the back of the queue, regardless of its length".
I've long thought this would be a good idea, as it's far easier to carry a load of clear plastic carrier bags than it is a big pile of trays (which is what it's getting to). I also find that random shoe screening is slower than just doing everyone's and being done with it (I commented this to the BHX screener a couple of weeks ago when I asked when getting ready if he wanted my shoes, and he said he wasn't allowed to decide until he'd put my bags on the X-ray. We both agreed this was silly and I just gave him my shoes anyway).