Although we don't believe in timing the market or panicking over market movements, we do like to keep an eye on big changes -- just in case they're material to our investing thesis.

What: Shares of GrubHub, Inc. (NYSE:GRUB) are trading roughly 8% higher this afternoon after peaking at a gain of over 11% near lunchtime. GrubHub seems to be part of a rising tide of mobile-centric dining apps following in the wake of's $2.6 billion acquisition  of OpenTable (UNKNOWN:UNKNOWN), which was announced this morning.

So what: OpenTable was bought at a near-50% premium its Thursday closing price, and GrubHub is currently valued quite similarly to the OpenTable buyout price -- its $2.8 billion market cap is within spitting distance of Priceline's $2.6 billion bid. Since both OpenTable and GrubHub help smartphone users get the food they want when they want it, investors who missed out on the OpenTable acquisition seem to be flocking to the similarly positioned GrubHub.

Now what: While OpenTable and GrubHub both serve hungry smartphone users and have similar valuations and their business models are somewhat at odds with each other -- OpenTable is targeted at users who want to sit down at a restaurant at a certain time, while GrubHub helps its users get restaurant deliveries from establishments that don't typically deliver their meals. GrubHub is also so new to the public markets (its IPO took place just two months ago) that it's somewhat less likely to be bought out in the near future. GrubHub's forward P/E of 200 is also nearly three times OpenTable's forward P/E of 75 following the acquisition, which may be too rich a price for potential acquirers to swallow. I'd stay on the sidelines for now.