Aren't there companies now that are making links to anonymous user names? Like at some point your real name gets associated with all sorts of anonymous postings.
None of this matters until it does and then it does.
Probably. I think people are complacent about this because they feel nobody would care enough to dig deeply enough on them to do things in ways that would impact them. And that may be the case now, but people are working furiously on automated tools that tie all type of information that can be accessed publicly together in such a way that it can be accessed instantly.
One such tool is Accurint
https://www.google.com/webhp?sourceid=chrome-instant&ion=1&espv=2&ie=UTF-8#q=accurint
For roughly $20, accurint will give me:
Every alias and AKA it has found you using. Sometimes I have found nicknames here that then led me to forums or other online posts, but that is rare.
Every address it has found associated with you. Imagine every company that has ever sent you a bill. More than a few are willing to sell their mailing lists, so it is rare that an adult lives somewhere that hasn't been captured.
Every other person that has been associated with those addresses at times contemporaneously with you.
Every phone number associated with you.
Everyone else associated with those phone numbers.
Every vehicle registered under your name.
Everyone else associated with those vehicles.
A list of possible relatives, their addresses, and telephone numbers listed to those addresses.
Everyone else associated with those addresses.
Every traffic ticket and criminal charge.
Every piece of property you have owned, how much you paid, who you bought and sold it from, and their contact info (this info is readily available from most counties for free).
Email addresses you have used. I think they get these from credit reporting bureaus. Your credit information requires specific authorization, but the additional information you provide to somebody pulling your credit (like where you work) is fair game. This is what leads me to forums because a lot of people like to list their e-mail addy on forums when buying and selling stuff.
Your employers and positions.
Any business you have ever been associate with in any type of ownership capacity. (this is also free online public information in almost all states, provided by the secretary of state).
Worth noting is that the above gives me a lot of data, but little context. For my job, forums were great to fill in context like few other sources. Why? Because on Facebook you are largely interacting with friends and family and many of those relationships have some real-life or off-Facebook component. An internet forum is mostly self-contained where all information you are sharing with your peers happens in that forum, so you get an ENORMOUSLY greater amount of exposition in posts. You don't tell your family how many sisters and brothers you have and what your dad did and where you live and where you live as a kid but you offer this information up whenever you need to be understood to people that don't know these details and a forum is full of that.
The amount of data available is going up, and the cost is going down. Right now, most employers probably do a google/facebook search for you, but I know some are using services like this, and as more employers become aware that tools like this exist, I am sure more will jump onboard.
I never used a service (accurint or its competitors) that provided me with forum usernames, probably because right now there is not a good place to aggregate that data. But I bet somebody out there is prying at those relationships in the data.
There is big business in the information game, and the process is moving towards more automation so people don't have to pay me to dig it up. The more automation, the more convenient and the lower the costs, which make it more likely that somebody will be pulling reports like this on you.
One final note on this subject. As part of a mortgage loan, you sign an authorization that allows, over the life of the loan, a large number of people (the lender, any lenders your mortgage is assigned to, mortgage insurers, escrow companies and others) to pull your (current and former) credit records, obtain your (current and former) employment and income, obtain current and former bank account information, and present for verification any piece of paper you presented to obtain the mortgage, which is a LOT. If you have a mortgage out for 20 years, that authorization you signed 20 years ago can be used to basically get current information of your whole financial life, even to entities that never had it in the first place- like the guy contracted to investigate your loan file for fraud by the mortgage insurance company you have never even spoken with. I don't know what you should do with this other than get creeped out by it.