JupiterResearch says a poll shows 60 percent of home Wi-Fi network users have enabled security on their networks: I've been hearing anecdotally from many travelers and urbanites I know--and seen in my own peregrinations--that it's much more likely to see WEP or WPA enabled on networks when you're trolling to kipe some service (29 percent of us have done that). The press release doesn't have much detail, as the company is selling a report with the information, but notes that WPA has made it easier deny outsiders network access.
The Wi-Fi Alliance will launch a big initiative this fall to push a new, unified method of turning on WPA through a simpler process that won't require creating a passphrase. Rather, the system will generate it and protect it in a variety of ways, requiring a short PIN or a button push to provide out-of-band confirmation.
I'm an active wardriver (which means I passively receive the beacon signals from wireless networks and map those) and those figures do match what I see on an average tour of a city. "Networks with WEP" is really winning over "Networks with no security", and other types of encryption (better than WEP) are also increasing. From a run this morning: 66% with WEP or better crypto, 21% of the total with better crypto (WPA).