What does that phrase mean? I couldn't find anything using a google search.

I'm not sure about sourcing, but it was recently used on the Stack Overflow podcast in Jeff and Joel's discussion of the profitability of creating plug-ins for another piece of software. Other considerations aside, one of the greatest threats to stability was if you created something so useful to the general userbase of the parent application, that the producers of the parent application would roll that up into the next version of their software, thereby rendering your cash cow redundant, e.g. a spell-checker for Firefox.

Joel likened this to snatching nickel from in front of an oncoming steamroller.

You might pick up a few nickels, but you might also get crushed. (I'm not sure how it applies here.)

He obviously meant that if you add useful, basic functionality to a major system or app (iPhone in the original discussion, Word here), don't be surprised if it is directly incorporated into the system/app.

the phrase "picking up nickels in front of a steam roller" refers to doing something dangerous for little gain.