I have recently had two questions involving a Telerik product voted down. Telerik namespace not found in deployed MVC3 application, and Very odd event behaviour for onChange on Telerik MVC DatePicker. I see nothing wrong with the questions and the only thing they have in common is that they are both tagged Telerik, a not too uncommon tag on SO. What is with this kind of behaviour? Is Microsoft one of the elite vendors that questions about their products are OK, but other vendors not?
You got one downvote... This is not suspicious behavior, and it does not indicate any type of "trend". There is no Microsoft-led conspiracy against Telerik or any other products/companies.
People can choose to downvote questions for whatever reasons they choose. The entire meaning of a downvote is expressed in the tooltip that you'll see if you hover over the arrow. It says:
And since downvotes are merely an expression of the personal feelings or opinions of the user who casts them, one can only assume from the examples that you've shown us that someone out there thought that your questions were "unclear" and/or "not useful". (I don't think research effort is the problem here, but who knows? Personally, I think the questions are fine and wouldn't have downvoted them, if that helps.)
So no, there's nothing wrong with either behavior—your questions or the downvote they each received.
Downvotes are anonymous for a reason. To attempt to label people who choose to retain that anonymity as "cowards" is quite offensive. There is no guaranteed relationship between downvotes and comments. They are left at the sole discretion of the downvoting user; you can leave negative comments without downvoting just as you can downvote without leaving comments. There's nothing wrong with either.
There is something wrong with calling the users who choose to do so "cowards", although it does highlight quite nicely why it is important that downvotes remain anonymous. In particular, the likelihood of retaliation. Here you are on Meta complaining about a single downvote (albeit to two different questions) and calling the user who cast that downvote a "coward". Imagine what you'd do if you knew who it was!