It's true. I have some pet peeves when it comes to UX portfolios (even some assets on the job). And I AM so guilty of these...in the beginning. Learning is a process...how well I know.

• Screen shots that are too small to read. Seriously why bother.
• Screen shots without any explanation. Context please.
• Wireframes without any details. I doubt you designed a static page...
• Portfolios with only pictures. What did you contribute? If you did it all, then say it.
• Under designed portfolio. Really, your a designer and you like your job, right?
• Over designed portfolio. Don't be too cute, too fancy, too "current-with-every-trend-happening-NOW", or too much (as in overwhelming amount of stuff on a page).
• Interesting or complex designs without the why. Any research papers, usability tests, a/b tests, heuristic evals, comparison apps, ...why did you finalize on the final design?

I probably have more...so this may be updated, but off the top of my head. Easy to spot a good portfolio.