If a search engine cannot load all the resources necessary to complete a page load because you're preventing it from doing do, then you can expect lower rankings, because people want the content.
Here's two scenarios for you to consider as a guest to websites:
You search for information about a dog and come across a listing in a search engine you like. Let's call that site http://woofexample.com. You then load the website and notice paragraphs of information about dogs but also large empty spaces, each one having a small broken picture symbol inside and the spaces are between the paragraphs.
You search for information about a dog and come across a listing in a search engine you like. Let's call that site http://bowwowexample.com. You then load the website and notice a few paragraphs of information about dogs along with images of various sizes and nothing unusual.
Which scenario would you rather be in? I'd personally pick #2 because it offers the best user experience and the people who run search engines appreciate (or at least should appreciate) webmasters who spend time to make sure their websites present full content to the guest. This means allowing the client browser to load ALL of the resources necessary to properly display a webpage.
You may want to read up on google Webmaster guidelines for more detail, but the point is, make the users happy and pretend the search engine bots are your users as well.