I guess it depends what kind of music you play. Pop stuff like Lady Gaga and Justin Bieber will always do well on the internet because it's all tied in to Twitter and YouTube. A regular guitar band will need to do something incredibly gimmicky to get the same amount of attention. Kings Of Leon had to sell out and become a poppy boyband to achieve a greater level of success, but even they didn't reach the heights of Lady Gaga.
At a grassroots level, based on my own experiences, you can play gigs for years and never get anywhere. It's hard to even start playing actual music venues (places where people exclusively go to watch bands, not pubs or backrooms) without any representation. A booking agent will get you gigs that are "closed off" to regular unsigned bands, but unless you are willing sink all your money into your band and give up your job to tour full time and sleep on floors, it's very hard to get anywhere by just doing gigs. I joined a band with a booking agent in London and while we did tour, we would have needed to go on the road full time to make the next step to increasing our profile (the band had been doing well before I joined, with Radio 1 sessions, NME coverage and TV spots). Added to that, London is supposed to be the music mecca of the UK ("London was calling!" they say), but you could do a year of gigs there and never get noticed. The standard of small gigs there isn't any higher there than anywhere else in the UK - if anything, it's lower, and that was a bit of an awakening.
I'd add the Joy Formidable in as a band that have broken through by relentlessly touring. They've been touring non-stop since mid-2008, when they put out the first EP. Their debut album only came out in January this year, and they've just kept going round and round and round. They've already done more US tours than you can count on two hands. People appreciate how hard they work and it's reflected in their presentation and performance.