[webmaven]

I've seen this approach used for evil (for example, fake female profiles on dating sites), and the gender-neutral version used on social networking sites of all sorts.

It's a hack, and not a particularly savory one. I'm not surprised it left the OP with a bad taste.

[Houshalter]

I remember reading that reddit started out with the founders posting tons of stories under fake usernames to make the site look more popular than it really was.

[webmaven]

Yup.

A more savory version I've come across in an online game startup is saturation bombing your daily AdWords budget within a very small window, thus ensuring that everyone who shows up finds lots of other folks to play with, leaving them with a good first impression of the game's popularity.