Spinorial: Actually, the earliest I recall, their keys were one per tier. Then they split them up, and started changing things around. The backlash came, I believe, when they introduced the direct-to-account activation, and they appeased the masses with the gifting mechanic. I'm actually really disappointed that they didn't opt to transfer the DRM-free versions with the gifts. It flew right in the face of all the anti-licence-splitting they so vocally professed. They should have allowed bundle-splitting, not game-splitting.
The direct to account activation didn't bother me as it doesn't restrict me in any way I'm aware of that affects me personally. Before I got a Steam key I could redeem myself or gift/trade, now I get a URL to click on to redeem or another one to gift to someone. Different mechanics but same end result for me.
If they came out with a bundle with N games in it and I wanted all of them and it was a single key, I'd have no problem with that specific purchase though because I want all of them anyway, but one key per game (or URL or whatever) is strongly preferred and not having that will cause me to skip some offerings for sure. It hasn't been a huge deal in practice though as none of their bundles have interested me in quite a while, while Bundlestars can't seem to stop putting out bundles that interest me. :)