I think as a mode of advertising, it's iffy. I also agree with what was said above about depending on who you mingle with.
I followed around 100 people, and have 80 followers and I TRY to mingle but every single person I followed just spammed the hell out of their followers.
Of course, it's more for long-term.
I know somebody who has 10,000 followers and they were complaining that they hadn't made a single sale or generated a single lead..took a look at their profile and all they did was spam. Not one personal message. Thing is, their followers were largely made up of spammers also.
*when I refer to spam, I don't mean true spam "I didn't ask for this". I mean constant bombardment of sales messages.