My thoughts on the linkshell vs company vs Grand Company are this.

 Linkshells are chat channels restricted up to 128 members at a time. We can have up to eight. In FFXI, linkshells became a way of coordinating activities and fulfilled the role of guild/clan/legion. This mentality carried over into FFXIV, thus people treat linkshells as a "guild". You may have a linkshell to find adventuring groups, one for crafting, one for International friends, one for role-playing, one for talking anything under the sun and kick back, etc.

 A Company is an official instantiated "guild" where exclusivity is expected. You only join one at a time. You are a name, a presence, in Eorzea, not just a pearl.

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 Company growing in rank. A company level.

 Company leves or quests that contribute toward company level and may provide "generic" company seals.

 Company choosing rewards based on company level that benefit company members in a multitude of non game-breaking ways: (i.e. +10% gil/seals from leves, +10% xp from monsters, -10% on airship/chocobo/repair fees, -10% weakness duration, -10% durability damage on death)

 Company ranks with customizable title. (i.e. a company may have a Leader may be called the Archmage, an officer may be a Wizard, and a new recruit an Apprentice).

 Company banks where permission can be set for donation and retrieval based on member rank.

 Company management tools to allow for a company message of the day, online/offline notification, invite regardless of distance, removing a member whether online or offline, promoting another to leader, promoting to company rank, setting privileges per rank, etc.

 Company seals can be used to promote Company level, to purchase unique rewards, or craftable materials.

Linkshells should have the ability to quickly chat between the different shells, such as /1 /2 /3.

Linkshells should not adjust chat position when a player is no longer part of a linkshell.

Linkshell management to allow remote invite and removals. Offline players should be removable.