UVa has traditionally had a large wait list for undergrad admissions. The Post collected data for the last 2 years from competitive universities that would release the data, which is at the link. The table at the end shows that UVa reduced the size of its wait list significantly from 2014 to 2015, to make it more realistic.
Interesting. Is the only thing to do for UVA when on the waitlist really just to send one email indicating you are still interested?