Unfortunately, this is an issue that’s fluctuated so much over the past 5 years that I don’t feel entirely comfortable giving a solid answer and feeling secure it will be the right one long term.
The current situation is that for google, most of the time this isn’t a problem. You can set up a site in spanish targeting spain, another in mexico and a third in peru, many with overlapping content pages and so long as the country tlds are unique (e.G. .Es, .Com.Mx, .Pe, etc.) and/or you’ve separately targeted the sites through google webmaster tools ( more on that topic here), you’re relatively safe from duplicate content filtering.
That said, bing is not nearly as sophisticated on this front (usually), though they are getting better
I don’t know how search engines like baidu, yandex or naver might handle this situation, currently – if anyone in the comments has expertise Dubai Business Fax List here, please do chip in. Given this, it’s often wise to choose either a globally-targeted site or biuld very customized sites to specific regions (even if there is language overlap). You can always use the cross domain rel=canonical if you want to “Share” content between/across sites and self-select which one google returns.
It depends whether you mean directly or indirectly
Directly, it will likely be twitter. Google’s ongoing animosity with all things facebook shows no sign of shifting and thus I’d say it’s unlikely google will start using facebook signals directly in the results. However… As we showed with correlation data, things that do well on facebook tend to do quite well on google, too. Indirectly, the ability to influence a Email Lists wide network on facebook, earn lots of shares, comments, likes and activity may indeed lead to very positive and influential second-order effects (links, tweets, positive content analysis signals, etc).
The service is a clear leader in many fields – marketing, politics, technology, investing, media and more – but it’s not yet a service everyone’s using (~100 million actives vs. Facebook’s 750 million). If it sees growth spikes, engagement increases and they become more ingrained in the fabric of “Normal” society, then they may indeed be competitive with facebook for influencing the results, on both first and second-order levels.