HumbleBundle force added every game I own.

Since all mine are activated, I haven't seen such happening.

Doesn't seem it happened for me, not 100% though

Nope, has not happened to me and I have some unredeemed games. I just unlinked my account just in case. That shouldn't happen though.

don't know what caused it but anyhow don't play any of them and send e-mail to humble bundle support. they'll sort it out.

I didn't had any issue, my unactivated keys are still there. I think I once saw a "redeem all" botton somewhere, maybe you pressed it.

I have a couple of unredeemed Humble Bundle games which have not appeared on my account.

I don't see any new games in my library, so no.

If proven true i find it very unprofessional of them

Let's see a screenshot of your account details!

https://store.steampowered.com/account/

Their TOS has this covered, but assuming it was a legitimate bug, I'm sure they'll correct it.

"Our obligation to deliver any Product to you shall be complete at the time when and place where you first receive the information necessary to commence download of such Product. In all circumstances it is your responsibility to ensure that the Product is correctly and completely installed on your computer. Once a Product is purchased and you receive the Product, it is your responsibility to keep the Product from being misplaced, damaged or destroyed, and Humble Bundle shall be without liability to you in the event of any loss, damage or destruction."

http://www.humblebundle.com/terms

I too don't see any new games in my library.

i've several unactivated games and, afaik, they all remain so

You were likely compromised and someone trolled you rather than stole your stuff. I'd recommend changing your password and taking the loss/gain.

happened twice for me...

Nope, didn't happen.

Nope, have several unclaimed ones under the current system and my account is linked.