"Anybody who has attended a few developer conferences has seen a long line of laptop bags against the wall at meals and receptions"
Just... stop doing that.
There are a couple of approaches. I'm that weird guy who keeps my laptop bag with me at all times (when I don't leave it at home, and if people are breaking into my home I have bigger problems). It's a little awkward to have a bag with you / under your table at dinners and such, but hey, we're all programmers, we can be awkward.
If you set out with the approach that your laptop is dangerous if it isn't in your hands, you quickly adapt to carrying it everywhere, or leaving it in advance in safe places like locked to your office table.
You can also set an admin password in your BIOS and disable booting to external drives, set a GRUB password, and lock your screen when you walk away. While it's not enough to deter a determined "Evil Maid"-style attacker who's willing to open your laptop, it's probably good enough. (This worked better on my netbook, which didn't have an easily removable internal drive, even if you opened the case.)
Finally, we could as a community figure out how the heck you're supposed to use the TPM and trusted boot and all this fun stuff. I would really like the ability to create a trusted container/VM on my laptop, and I know the hardware technology exists, but I can't figure out how to use any of the free software support for it. It should get built into the desktop the way things like NetworkManager are.