I would agree, but I think people's idea of deemed worthy is drastically different and I hope it does not become too much of an issue here. The way I look at it is my pledge of 1BTC is a minimum donation, more to Bitcoin than the charities themselves, as there are a few charities mentioned that I would not donate to outside of Bitcoin100. The charities that I like more will get more from me separately. Like archive.org, which I sent 1 to already and will send more if/when they add a button directly to their donation page.
I certainly understand the sentiment and would love to do the same. I expect I'd have no problem with pretty much all organisations that would be considered for support. I would however refuse to donate to organisations such as Monsanto or the RIAA and for this reason alone simply cannot say "I pledge 1 BTC to any charity/organisation which adds a Bitcoin donation option".
Generally, I won't be upset if Bitcoin100 money ends up going to causes I wouldn't usually donate to. As you noted, such pledged money is much more like a donation to Bitcoin itself. If a cause comes along that I really do want to donate to (TOR, Free software foundation, archive.org) then I will make a serious donation on top.
I would be dismayed if the Bitcoin100 didn't manage to get 100 new charities to accept Bitcoin. It would be a great shame for us to only get through 5 or 6 charities before fizzling out due to there being too much caution. Just my thought though.