Perhaps the Semantic web community is doing a bad job at making these topics exciting, but the concepts still stand or else there wouldn't be an entire branch of research dedicated to them.
So in my opinion we should be more positive about the very valuable knowledge being generated by these communities, and perhaps transform it or create tools around them to make them more user friendly and more exciting.
I guess overall what I'm saying is that the concepts of the Semantic web are valid no matter the cumbersome culture around them. We should judge the ideas not the tools.
RDF is for databases what Turing machines are for computation: the minimal model that abstracts away as much as is possible without sacrificing capabilities but ignoring anything performance (memory usage, execution time) related.
1. I'm not saying the sem web concept is useless but that poor quality and unnecessarily high costs make it a worse deal. More practical focus on specs and solid software engineering would avoid making that trade-off worse unnecessarily.
2. Many topics which are of interest to academics either aren't generally useful and too many academics are dismissive of mundane concerns like software engineering. My first point falls solidly into that latter case. The former case isn't proven – it's entirely possible that we'll eventually see something interesting develop with more time, although as another commenter pointed out, it's likely that we'll see something different which uses the good parts but doesn't give up as much for theoretical purity. Of course, it's also possible that they'll spend more time having academic debates over HTTP range-14 and what will actually be adopted will come from outside the current semweb community entirely – after all, the “Web” in SemanticWeb refers to a technology which saw rapid growth due to ease of adoption, even though the academic hypertext community wasn't impressed because it was too simple.
In every case, more attention to building useful tools would massively increase the number of people working with semweb technology and lower the cost for everyone doing research. Everyone who wants that class of technologies to succeed should be focused on lowering that barrier to entry.
RDF isn't just XML! Look for this tool that does JSON serialization!
* looks for such a tool, finds a broken mess
It seems like the single most useful thing which could happen for adoption would be cleaning that up: a clear use case which isn't already well solved and a good tutorial outlining the benefits with non-trivial examples which follow the current standards, validate and introduce production quality tools. If any of that exists, it's managed to stay completely off the mainstream computing radar, which is a pity given the number of smart people who've poured considerably amounts of time into it.
As an example: a lot of the RDF community hated schema.org when it was announced because it used HTML5 microdata instead. If you were a web developer, the case for microdata was easy: add a couple of simple HTML attributes, use one of multiple high-quality validators to test your markup, and Google/Bing/etc. would return better search results for your data. At the same time, it was daunting to write an RDFa equivalent because there were no complete, current, non-contradictory docs and examples, the W3C validator had been broken for over a year (it was at least up, unlike all of the other online validators) and nothing actually supported it so you'd be investing hours or days instead of minutes in the hope that at some point in the future it would become useful. Most people with jobs to do are just going to wait until the demand side of that equation is more favorable.
The best example of linked data in widespread usage is Facebook's Open Graph markup but it appears that almost everyone simply stops as soon as they get the desired results in Facebook and, predictably, almost none of the examples actually validate because of tooling and cultural issues.