The list of "legitimate" service providers who require screening/deposits is longer than the list of those who don't...personally, I have no objection sending an advance to someone when I can spend less than 10 minutes to find a website, active social media, positive reviews/comments etc.
This is not really the case being discussed in this thread, although "close". Despite having links to SM in her ad, neither is what I would consider "active", with only a single post, nearly a year ago. As Mikeyboy said above...verify, verfiy, verify...and if/when in doubt, skip it.
All these deposit scams are coming from unverified sources within LL. I've fallen victim myself, and have learned from that. My point (like Raven mentioned), is don't let the deposit itself turn you away from a potentially great encounter, just be confident you know where it's going...a legit SW is not going to risk their livelihood over a deposit...