Drugs companies were prohibited from advertising on television until not so long ago. There's even a special law: http://en.wikipedia.org/wiki/Prescription_Drug_Marketing_Act...

Arguably, that is the crux of the 1st Amendment issue -- government regulation of speech - including that of "evil" or "unpopular" drug companies -- is a slippery slope.

The past few years seem to indicate that we're slipping up the slope, then, as what was once prohibited is now allowed, both in the case of prescription drug advertisements and corporate political speech.

Compare with the following phrases: Prohibiting forgery strays dangerously close... Prohibiting defamation strays dangerously close... Prohibiting Ponzi schemes strays dangerously close...

I can accept that regulation of speech is inherently suspect, but not that it's inherently bad. The reasons for regulating this kind of advertising are pretty clear to me.

Prohibiting slander, libel, and inciting imminent lawless action are also technical violations of the first amendment. Society tolerates these rules because they provide even greater value than the freedom of speech alone.

In this case, I agree that prohibiting advertising is a first amendment violation. Instead, we should simply disallow all outdoor advertising and advertising that is broadcast on the publicly-owned radio spectrum.