I do this all the time and so far it has never come back to bite me in the behind. That being said, I thought I might be able to get some information on whether or not this is potentially risky. Here's the scenario.

I make a starter and end up leaving it on my kitchen counter all week. If it sits for more than a day or so with no real activity I usually add some sterile wort to keep the yeasts active. Some times I have a nice big starter on my hands by the time I finally get around to brewing. This is essentially small scale brewing without the hops, right?