Here are some hard facts I have found out:
A query on "wordpress 2.7 vulnerability" shows 29,000 results while "wordpress 2.9.2 vulnerability" shows 11,800 results.
WordPress 2.7 was released back in February of 2009 -- we're a year and half practically away from that time.
There's nearly 3 times as many vulnerabilities with WordPress 2.7 as WordPress 2.9.2.
There were a total of 2,181 bugs/problems/issues/concerns that were closed between 2.7 and 2.9.2.
There were also several jQuery differences between 2.7 and 2.9.2 which could make jQuery functions fail.
Here are all the bug reports filed between versions 2.7 and 2.9.2:
Starting from 2/10/2009 when 2.7 was out:
http://core.trac.wordpress.org/query?status=closed&group...
672 bugs/problems/issues/concerns
http://core.trac.wordpress.org/query?status=closed&group...
74 bugs/problems/issues/concerns
http://core.trac.wordpress.org/query?status=closed&group...
43 bugs/problems/issues/concerns
http://core.trac.wordpress.org/query?status=closed&group...
786 bugs/problems/issues/concerns
http://core.trac.wordpress.org/query?status=closed&group...
54 bugs/problems/issues/concerns
http://core.trac.wordpress.org/query?status=closed&group...
1 bugs/problems/issues/concerns
http://core.trac.wordpress.org/query?status=closed&group...
5 bugs/problems/issues/concerns
http://core.trac.wordpress.org/query?status=closed&group...
14 bugs/problems/issues/concerns
http://core.trac.wordpress.org/query?status=closed&group...
2 bugs/problems/issues/concerns
http://core.trac.wordpress.org/query?status=closed&group...
505 bugs/problems/issues/concerns
http://core.trac.wordpress.org/query?status=closed&group...
25 bugs/problems/issues/concerns