Being smart and knowledgable about lifting does not necessairly mean you have to be big yourself.
Have a look at this video of strong man Mark Felix taking advice from his strength coach who is a 60yr old (or so) small man. But he knows his shit and apairently mark has made a lot of progress this off season since he has been working with his new coach.
http://youtube.com/watch?v=3pyAmrAQc4E&feature=related
On the flip side I've seen larger men giving horrible advice to people at the gym, telling them t do stuff that will seriously get them hurt.
So the answer is I will take advice (or at least listen to it) from anyone if it is given to me. It is up to me to make the decision if that advice is correct or not.