[Cthulhu_]

They didn't need to; Hotmail offered free e-mail accounts which was unheard of at the time; Gmail went viral for offering 1GB of storage which was unheard of at the time. The latter also had scarcity with its invite system, I'm not sure if that helped make it more popular or not. Definitely helped prevent it from collapsing under its own success though.

Anyway, I think any service now that shows up offering something used by many that is now paid for free will become popular on its own.

[ako]

That 1GB storage comes at a cost, which is basically a marketing cost. You give something away for free, in the hope it will generate word-of-mouth marketing. That free thing you're giving away is coming out of your marketing budget.

[ChrisRR]

Gmail didn't just offer 1GB, it also offered the ability to search through emails which I don't think any free service allowed you to at the time

In 2004 that was pretty amazing

[marcosdumay]

Yahoo had search. The Gmail one worked a bit better, mostly because you could automatically tag things, but it was not unheard of.

[xtracto]

Gmail had plenty of marketing when it started: Both the '1 GB account' and the "Search don't Sort" snippet where heavily pushed through several marketing channels at the time (paid articles, Google search homepage, among others). Not all marketing is "ad banners". For example, all those Businesswire articles are pure marketing and advertising.

[eezing]

The killer feature was archive.

Growth was viral. Only cool people had Gmail.