Need advice on having customer stores running on my subdomain

[schof]

We have an online store product and we're working on the SEO for our new domain (foo.com in this example.)  Our customers have the ability to change the domain of their store but many of them will likely stick with the subdomains we give them (store1.foo.com)

We could potentially have thousands of stores soon using our subdomain.  Each of these stores will have a very small link at the bottom to our own domain but other than this, the content is completely user-generated and not under our control.

Are there risks/problems associated with this type of strategy?  If so, could we perhaps avoid them by using robots.txt to block entire site until they change to their own domain?

TIA,

Sean

[HiveDigitalInc]

First off, the biggest concern will be spammers. Use a good captcha system like reCaptcha or OpenCaptcha to control who signs up, although charging money is the best way to keep them out.

Second, don't manipulate the anchor text at the bottom of the user generated stores, just use your brand name.

Third, I wouldn't be hugely concerned about it being a subdomain. Think about all the spam on blogspot and wordpress.com. You won't enjoy the authority status at the beginning that lends them some buffer against the spam, but if you control it at the beginning you should build up your site enough that you can weather some crap making it's way through.