<s>
Asymmetric	B-General_Concept
follow	I-General_Concept
refers	O
to	O
a	O
social	O
network	O
allowing	O
many	O
people	O
to	O
follow	O
an	O
individual	O
or	O
account	O
without	O
having	O
to	O
follow	O
them	O
back	O
.	O
</s>
<s>
It	O
is	O
also	O
known	O
as	O
asynchronous	B-General_Concept
follow	I-General_Concept
or	O
sometimes	O
asymmetric	O
friendship	O
.	O
</s>
<s>
Asymmetric	B-General_Concept
follow	I-General_Concept
is	O
a	O
common	O
pattern	O
on	O
Twitter	B-Application
,	O
where	O
someone	O
may	O
have	O
thousands	O
of	O
followers	O
,	O
but	O
themselves	O
follow	O
few	O
(	O
or	O
no	O
)	O
accounts	O
.	O
</s>
<s>
In	O
September	O
2010	O
Facebook	B-Application
started	O
experimenting	O
with	O
a	O
similar	O
feature	O
,	O
which	O
Facebook	B-Application
calls	O
"	O
Subscribe	O
To.	O
"	O
</s>
