There is a common misconception in SL that RLV is dangerous.
If you refer to dangerous as getting your clothes taken off without being prompt by some sort of dialog message then well yes it is dangerous. However if you refer to stealing, deleting or spying it is not.
Any script in SL has the capability to spy on your local chat messages and location. RLV enabled or not. In this regard RLV does not provide any additional functions apart from maybe making it a little easier.
RLV can not read your private messages (IM’s) just like any normal script cant do that.
RLV cant take your money.
RLV cant delete your inventory
Scripts can be dangerous. This however has nothing to do with RLV and you shouldn’t just attach or rez any scripted object you get. Especially when some random unknown person sends you something.
RLV brings many extra features to SL making things like wardrobes, group changers, sitters and other things possible. The developers of RLV do however care about your safety and you may expect that features like taking money, reading IM’s will never be implemented. And if the contrary would be the case its is extremely likely that LL would ban a viewer with there’s abilities.
As a scripter with experience creating RLV enabled products i know all the RLV commands that are listed on the official wiki here: http://wiki.secondlife.com/wiki/LSL_Protocol/RestrainedLoveAPI
If you are not a scripter of have no experience with RLV its very likely that the page mentioned above looks like Chinese to you (unless you actually speak Chinese). You should however be able to get a good indication of what RLV can do. And especially what it cant do.
Now there obviously is a reason why these RLV features are not build into the standard viewer and why they are off by default. But just keep in mind that this has more to do with not ending up somewhere naked then actually being dangerous in the sense of stealing, deleting or spying.
If you want RLV enabled or not is up to you. Just remember, RLV can be switched on or off at any time by just doing a re-log and going to preference.