That's ridiculous, you don't just tell someone "say yes or no.." without allowing for an explanation when the subject is open for debate.
Yes, he should have caught the ball but it was one friggin' play for crap's sake! I haven't heard anyone around here complaining about the fact that Ricky Williams rushed for 1 yard on 6 or so carries. Based upon the logic that you and the others are espousing here, Williams should be sacked because he's dont absolutely nothing in preseason. Now, we all know that is not the case and that once he gets going there will be no problems. Likewise with Chambers; once he and Jay get some game time under their belts I have no doubts he's going to be fine.
Also, what has Thompson really done in any of the preseason games? The answer is not a lot yet people are still calling him an excellent offseason acquisition based upon his TC performance. Yes, he's done great in TC and made two nice (short) grabs last night, but Chambers also made a nice grab over the middle and played a lot less. Chambers, by all accounts, has also had a very good TC so really, why concern yourself with what he hasn't done in some VERY limited action in a couple of preseason games.
Remember, most receivers don't break out until their third years so quit worrying so much about what Chambers hasn't done in his limited time on the field and focus upon what he WILL do once the actual game time comes around.