Yes and Yes.
I didn't see the first meeting between Sonnen and Silva but in the second meeting there was a point in the match where Silva was casually walking backwards across the ring with his arms down by his side not defending himself. The rest of the fight Sonnen was bullrushing him and the entire first round Silva was in guard.
You should probably go watch the Belfort fight again. Multiple times he had his arms down not defending himself because Belfort wasn't doing anything...
http://vimeo.com/22345665 The first punch Belfort threw came damn near 3 minutes into the round when Silva was dancing around with his hands down. The fight lasted 4 minutes, you can bet your ass he would have continued doing it.
He'll wait til he thinks he's seen your best and feels you cant touch him and gets cocky. It cost him this time.
EDIT: Watching a replay of their first meeting and by the 3:30 mark in the first round hes doing it. Hands down taking shots to the chin.
EDIT 2: Just finished watching the whole fight and a more appropriate question would be... Did you ever see Silva with the opportunity to do what he did with Weidman? He easily spent 95% of the fight on his back because Sonnen, a wrestler, had no interest in sitting back and going toe to toe with Silva.