This answer is from Emmanuel Mwangi, a Project & Platform Manager at CUC Services:
Long load times.
I can’t stress how often I’ve seen sites with great design and seemingly great functionality get less than stellar results simply because they didn’t look at the load times as a part of how functional the site was.
Patrick Neeman is Director of User Experience at Jobvite, a social recruiting platform and runs both the UX Drinking Game and Startup Drinking Game | More | Contact
If you're a UX Designer in San Francisco, ping me at Twitter. I want to add you to a list I have there.
