Most of the safety concerns in an online relationship are based on male dominants because they are the biggest threat, but there are some submissives out there who play the part too. Not as dangerous as male doms maybe, but just as destructive to a BDSM relationship.

Over-eager

These submissives are the ones who want to "suck the cream out of your cock" in their first contact with you. They tend to talk dirty and push for your dominance from the word go. They also usually won't give you one bit of real information about themselves. Not even a first name. These people are usually just looking for a quick online thrill and have no intention of building anything with you.

Yeah I've done that...and with twenty people watching.

This person has every toy under the sun and has participated in every decadent act known to dom...and is 22. Yeah okaaaay. Watch out for these subs folks. Chances are good it's crap and you'll get a lot of I can't find it's and I lost it's when you ask them to demonstrate something. If you're a new dom someone with experience can be appealing, but makes sure the submissive has experience and isn't just living in a fantasy world.

The amazing lightning sub

You're in the relationship online and because it's new you have no visual on the submissive, but you're giving her orders and she's following them...you think. Tasks take time and sometimes you'll get a sub who can smack her ass ten times with a ruler in under 2 seconds. If you aren't sure whether or not the submissive is actually doing what you want give her tasks that you have timed yourself so you know roughly how long it should take. If the task gets done really, really fast you may be dealing with this person.

There's more of these too and I'll add them as I think of them.