First of all, a subdomain structure has no negative effect on the SEO or that page, or a complete site, but it has to be done right. However, there are many factors that could come into play here, such as "what would Google think if they did a manual review of the site and subdomains?"
If your feeling is that they look like very obvious attempts at SEO, then yes, do something about it, but using subdomains is sometimes necessary. I use about 8 subdomains for my site, but that is because I use a single page design so I am limited in my options.
That said, I have some great rankings for these, with many 1st page and top 3-4. This is because I can create a site (subdomain) that is very highly targeted.
Not many will take this route for SEO though - there generally isn't the need. You can normally do just as good a job with a normal site structure.
-Andy