The title of this post can probably be said of many people - in certain circles, me included. The interesting thing now is the "certain circles" part. It was a lot easier to make dumb mistakes as recently as a decade ago - the mistake happened, you moved past it, people tended to forget.
That was before the net, before social networks, before blogs. Now, any mistake you make will be recorded for all time, so long as anyone is there to see it. More to the point, it's immediately findable, via the wonder of Google. If you work online at all, you have a personal brand - whether you like it or not.
That means that everything you do in public will add to your personal brand.
That gets me to the best (current) bad example of this: Matt Aimonetti. He gave a controversial talk at a recent Ruby conference, and - for the foreseeable future, that's what he'll be known for. It doesn't matter what you think of his slides, or of how it's all been perceived. What matters is that he's known for that, and it's going to drag behind him forever. Right now, the second hit on a Google search for his name turns up his explanation for that talk. Never mind his explanation and whether it's good or bad; the important thing is this: he's now tagged as controversial, and will likely stay that way for a long while.
That's what happens now - you build your personal brand at all times now, and no public (and it's hard to know what isn't public anymore; consider Facebook and photos/videos) actions are guaranteed to disappear from view. Anything I did in college or in my 20's lives on in memory only. It's not like that anymore, and anything I do from here on out is "on the record" as well. It may not be fair, but life isn't fair - it is what it is.