the threshold of 500 connections as a convention of participation in the realm of linkedin

the conventions of participation can have a peculiar meaning in a social space.

within the space in linkedin, the professionals' network, when passing the threshold of 500 connections, the exact number of a member's connections is altered from the exact number into "500+". 

this rule (convention) set by the designers of this site has mysterious meaning: is this a token of strength ( apparently, you are well connected) or is it a sign that you do not take your linked connections seriously (assuming that the number of meaningfull connections is limited to under 501)?

what is the meaning in this delineation of the number 500?  why not create the space for a more open convention and let users set the delineation number themselves?   

it remains an interesting feature of this digital social space. and holds inspirations for designers and participants of any space.