I started working as a Developer Evangelist about a year and a half ago, and was having a pretty nasty problem dealing with contacts myself. I keep meeting people all the time, and want some way to:

* Have their contact info auto-imported if I add them as a friend in SOME WAY: either by emailing them, tweeting them, messaging them, whatever.

* Have all my contacts synced into one centralized data store (Google Contacts, in my case).

* Merge and remove duplicate contacts so I don't have to deal with 50 entries of people...

What I ended up settling on is really working well for the past year or so.

I use Google contacts as my primary datastore. I then use FullContact (free): https://www.fullcontact.com/

FullContact will hook into everything, eg: Google / Twitter / Facebook / LinkedIn / etc., grab EVERYONE'S contact info, and merge it into one record, then merge that back into Google contacts =)

Would highly recommend it.

My experience with FullContact was one of constant duplication of data (at both record and field level for both exact and inexact matches. I.E. two contacts representing the same person with say, differences in first name -- Jon vs. Jonathon for example -- would often result in two contacts with a combination of fields from each of the originals. Didn't have to be name. Address, for example. "Road" vs. "Rd" confused the hell out of FullContact routinely...), totally useless features to resolve (in particular) non-exact duplicate matching, and an absolute contempt for any manual curation at all.

Essentially it made mash of my contacts, wouldn't let me correct them either in their UI (with features built exactly for that), and or in any native apps, more than a year on I'm still nowhere near cleaning up the mess.

All they had to say about it was that "synchronizing contacts is a hard problem", or something to that effect. No effort to repair/undo the damage, no suggestions on how to avoid future problems -- sorry we ate your data, sucks to be you.

This is exactly how I manage my contacts. It works super well.

I also started using the full contact mobile carddav sync - which has worked super well.

The card scanner with fullcontact is also nice, but paid.

Get everything in Google Contacts and use the webapp (https://contacts.google.com/) to merge contacts. It has the ability to suggest merges and it's easy to do the leftover ones manually.

Came here to say this. Whilst I don't particularly like sharing my contacts with the big G-Brother, I do find their user interface and the associated Android apps extremely good.

I tried to move to ownCloud, but I just couldn't bring myself to make the full move over since my email was still on Gmail.

Just as I had decided to move to Fastmail, Google came out with Inbox. The Android Inbox app is just too good to leave now.

https://contacts.google.com/u/0/preview/all the new google contacts can help you in categorising contacts finding duplicates and delteing them aswell

I tend to combine personal & business contacts together.

Recently came across the Free Hubpsot CRM, while I've yet to give to get it a test drive, the demo looks interesting > http://www.hubspot.com/crm

Given that I keep a very close group of friends, the default iOS Contacts app w/ iCloud works.

For those with large groups of people/information, go with Google Contacts.

iCloud contacts synced across several Macs/iPhones. I use GMail through in the IMAP interface and keep the contacts syncing here disabled.

Same, all contacts in iCloud. If @icloud.com wasn't my primary email then I would use Google Contacts.

Just don't use multiple systems, it will end up making a mess.

Google contacts as well. They have greatly improved the integration with maps in the last year or so.

Google Contacts, synced everywhere. Liberal use of fields for organizing/grouping/searching.