It could be lack of confidence, but it could also be that they just want to cash out.
To some people, a few million might be more than they'll ever need or want. Or maybe they just need cash right now (pay off debt, start a business, upgrade lifestyle) and a few million is enough.
Tesla was founded in 2003. That's a long time to wait for any kind of return, and some people are going to be impatient.
http://www.sec.gov/cgi-bin/own-disp?action=getissuer&CIK=000...