There are lots of factors and there is a good article in the Tribune about those factors.For example, my north side neighborhood has lost people while having a price explosion.  

Around 10pm, the neighbor heard an explosion and looked to see the house on fire.

What people are saying is that there's been an explosion of people getting told that wholesaling is an easy, low cost way to get into real estate investing and there are people out there training people to make offers on houses that they cant buy, market them for 30 days, then if they cant sell them just walk away. 

Although I am unaware of the facts, I would expect that REI's explosive incident was the result of somebody not following procedure by putting out all gas pilots or other sources of ignition.

You should not have to invest in far flung (from each other) properties in order to build a desired portfolio.I don't expect an explosion in Highland Square, things don't swing that hard or fast here.

While growth may not be as explosive as it would by doing as many deals as possible with the money available, this seems like a rather efficient way of going about it.

For my part I try  to screen tenants well enough I don't get explosions and smoke damage very often.

The cleanup from the digester explosion a couple weeks ago.

Population explosion, positive business outlook, lots of cheap properties, less competition, nice weather

If so that's some explosive sh.. they got there... :)