There have been several meta posts that received net downvotes, including:
My impression is that these downvotes were meant to express disagreement or a "no" answer, but I don't think that's the right way to use downvotes here. In fact, downvoting questions that you disagree with is arguably a bit rude.
The What is meta? How does it work? section of the Help Center states:
Like normal Stack Exchange sites, Meta allows members to vote on questions and answers. For most posts, votes reflect the perceived usefulness: well-written, well-reasoned, well-researched posts tend to get more attention and more upvotes. Highly-voted and frequently-linked posts may become part of the community-curated FAQ or codified as part of the site’s Help pages.
In addition, note the text for the tooltips on upvotes and downvotes:
Upvote: This question shows research effort; it is useful and clear
Downvote: This question does not show any research effort; it is unclear or not useful
This text is there for a reason, and represents the meaning of these votes. Indeed, this issue has been discussed at length at Stack Overflow meta, and the text above represents the current consensus. See this answer on Stack Overflow meta, for example.
The problem with downvoting questions that you disagree with is that it discourages good discussions. People are less likely to post questions when they end up downvoted, so downvoting good questions to express a "no" answer sends the wrong message.
So the bottom line is that a vote on meta should mean roughly the same thing that it does on the regular site: it pertains to whether the post is clear and meaningful, and has the potential to generate a good discussion. Upvote questions that seem constructive, and downvote questions that seem unclear or off-topic. But please do not downvote good questions that you happen to disagree with.