Contests and giveaways have definitely become more common lately, and HUBGFE has been a major impetus for the change.
As a general maxim, Mr. Monkey is absolutely right. But, this isn't necessarily like any other business.
An argument could be made that responsible advertising is necessary, much like for gambling, tobacco and alcohol. Sex is, after all, a vice.
The major downside I see (besides encouraging hobbying amongst those who may not be well-suited for it) is that contests require the winners to forfeit their anonymity.
Discretion and privacy is key part of this hobby. Those values seem to have been lost, much like in general society. Part of it is because hobbying is more open and "socially "acceptable". But I suspect also because many guys haven't thought through the consequences of being open about their hobbying. Also, to state the obvious, losing your anonymity not very conducive to writing frank and critical reviews of bad providers. The integrity of review boards thus suffer.